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FAQs on the Hydrozoan Compatibility & Control

Related Articles: Hydrozoans, Cnidarians, Fire Corals, Stylasterines, Hydrozoan Jellies, 'Coral' Compatibility: On Reducing Captive Negative Interactions Cnidarians by Bob Fenner, ppt. vers: Cnidarian Compatibility: On Reducing Negative Cnidarian Interaction Parts: 1, 2, 3, 4, 5, by Bob Fenner

Related FAQs: Hydrozoans 1, Hydrozoans 2, Hydrozoan Identification, Hydrozoan Behavior, Hydrozoan Selection, Hydrozoan Systems, Hydrozoan Feeding, Hydrozoan Disease, Hydrozoan Reproduction, Medusoids/Jellies (Ctenophores, some Hydrozoans, Scyphozoans): Jelly Identification, Jelly Behavior, Jelly Compatibility, Jelly Selection, Jelly Systems, Jelly Feeding, Jelly Disease, Jelly Reproduction, Fire Corals, Lace Corals, Stinging-celled Animals

Some Hydrozoans can even sting echinoderms.

re: Can't ID hair like growth in reef aquarium(SMALLER SIZED PICS)     9/6/17
Mr. Fenner
Here I bought a stereo microscope and took pictures of the pictures of the hair like growth being told. Hydroid digitate, Bryozoan Bryopsis, algae of unknown... Can someone please help me now??
<Mmm; well the color, strands remind me of algae... are there cell walls in the strings? That is individual cells making parts of the strands? If not, perhaps a blue green "algae". The expanded tips remind me of the ciliate Vorticella... how big are these? Could be a digitate hydroid, but so green?
Sorry, can't make out more here. Bob Fenner>

re: Can't ID hair like growth in reef aquarium (SMALLER SIZED PICS)     9/6/17
Some are 1/4" some maybe 1" but they come back quick...
<Umm; these are digitate hydroids... I'd be removing them>

Let me mess with the new Gadget it says up to 600x. I just held it with my hand and focused as best as I could I'm going to suction it down to a piece of glass I did add some distilled water to it I pulled it with tweezers from the base I
was hoping you could identify it by the circle tips at the ends of the object it looks like a red blood cell but green this is what they look like at there latest like largest... 1" tall Max. Look white not matter if I use a blue flashlight or if I use a white flashlight they look the same until I pull them out of the water then they are green right away I don't know if it's the oxygenation or if they're just green and look white but they have no feeding response when I feed my Montipora wouldn't a did you take hydrated have a feeding response to Reef Roids or Coral Frenzy or even Cyclops I see no change in anything actually the ones that have peaked in size have ingrown no more but if I were to pull them off or toothbrush them they would come back not as fast like tall wise but they come back on the Fred I brush them off when they were very small and within two days they're still back to their very small stage of maybe one 20th of an inch did you take my droid have a feeding response to reef Roids or coral frenzy or even Cyclops I see no change in anything actually the ones that have peed in size haven't grown no more but if I were to pull them off or toothbrush them they would come back not as fast like tall wise but they come back on the Fred's <?> I brush them off when they're very small and within 2 days there they're still back to their very small stage of maybe 1/20 of an inch. ..
<Pull the affected rocks out... dry>
if I can't figure this out I'm going to trash the library and then quarantine all my coral into a small 22 gallon frag tank because I'm worried that if I toothbrush this stuff off put them into a new tank it will just start the process all over again even though I'm using dry live rock next time or maybe I will just frag pieces of SPS that don't have any
near it but it's the track of philia that I don't know if it has these things on the small base underneath they don't grow on any fleshy Parts only on hard surfaces except glass... I noticed them growing on my overflow wall there is none in my refugium skimmer compartment because which is weird I have a 300 watt Mars light and a macro reactor and a CFL light growing some red color for red kelp tree like red grapes growing on a vine None but in the display...
<Thank goodness>
If I can't figure this out I'm going to most likely have to throw away a lot of corals that I've been nursing back from that product vibrant liquid aquarium cleaner and caused my anemones to basically shrivel up and it did nothing to this stuff after five doses I will try to get a better photo more detailed of the cell walls I mean the box of this microscope stereo microscope shows this thing looking at organisms not just maybe that's the picture I took of this stuff was maybe 40-50 X I mean looking at a hair is not that impressive when it advertises 600x maybe it's the distance I had it at it was too close Maybe I know it wasn't too far away... Just another question I bought some live rock drive from BRS.
<... see others opinions.>
The curing process. Just sit in barrel for few months small WC every week maybe and when no nitrite there ready? But how long do u leave em in there so there actually live and not just the decay wearing off and no po4 leaching.,. Also when I start so I have to seed with i.e. Biospira or an alrdy cured LR (NOT ONE OF MINE) even though some have these things on them while some but taking the risk isn't my biggest thing. I notice they don't sting cut irritate the sps and stunting growth. I have my macroalgae reactor running now and I also reinstall my algae Turf scrubber which the vibrant aquarium cleaner people told me to take off line so I'm hoping after that I've already
noticed a tripling of my Chaeto that I put in there a very small amount that you twist tie onto the plates and I'm also going to reinstall a new UV light I haven't had a UV running for about 8 months now but I think a recent tail rot and a Popeye incident in two separate fish I think UV would not be a bad thing
<Is a good thing>
and maybe when I toothbrush these things off it might stop the spreading of these or regrowth because the spores if any will die once they go inside the UV chamber fingers crossed thanks for your response and if you could please reply about the live rock curing that would be great thanks again you guys are wonderful for taking the time to answer regular folks like me that sometimes the answers might not even be there ever.
With much appreciation
Matt Macri
<Welcome to my input. Bob Fenner>

re: Can't ID hair like growth in reef aquarium (SMALLER SIZED PICS)     9/6/17
What about taking one rock out... Putting in a bucket of tank water with heater and pump... Cover it dark for three days and see if it dies..
<Mmm; not likely to die this way; but go ahead and try it>
How long can you dark out a tank safely without killing Coral?
<Depends, but likely the corals will die at about the same rate/exposure>
Ppl do it for Bryopsis etc.. I can hammer a piece of rock that the top half has the largest strands of this stuff.. it's a large branch rock with s large green Monti growing from a small ledge in the middle of it.. I was thinking of
basically halving it and black it out for 3-4 days and if it kills it.
It's an algae and I should do it to my whole tank....
Your input?
<Physically systematically removing, scrubbing off (and rinsing) outside the tank is my fave, direct approach... There are folks who advocate chemical means of burning, sealing... There are some potential predators including Nudibranchs, Seaslugs, Urchins, possibly fishes (e.g. dwarf angels) that might consume this pest>
I've never had a pest issue in 2 years I always found natural remedies like Emerald crabs or Turbo snails are sea cucumbers to keep mice and overturned or Nassarius snails to do the same thing bristle worms to eat overfed food always having a quarantine tank at Bay in case something happens always not being cheap on equipment even though I'm on disability but I save my money rather than buying cheap stuff I buy the good equipment this way it doesn't break or electrocute me or there's all kinds of stuff that can happen but I also buy a backup that's less expensive just in case... I just don't want to have to somehow take my fish somewhere else to a fish store which I can't monitor mean for all I know they could be breaking out and diseases and dying cleaning my tank out putting my Coral in a small frag tank with an acrylic box filter and basically scrubbing my tank with water and bleach and then scrubbing out my sump as well..
Done cycling my tank curing my live rock which isn't going to be new dry live rock once it's cured I have to re cure it so there's no phosphates linking or put it in my tank fish only for a month or two while the phosphates Leach out and then put my corals back in my tank once the phosphate start reading zero again that's a very very long and tedious process and I would have to find a place for all my snails crabs cucumbers pet shrimp of many sorts but I have a quarantine tank that is medicine free I could just add a few of the bad live rock in there to give them places
to hide and just Neil
throw some food in there once in awhile some algae Wafers some other kinds of food just to keep him alive and sand on the bottom for my Tigertail cucumbers one is almost 2 ft long and the other is about 10 inches and I definitely don't want them to die them are one of my favorite things to look at when they come out
<Bob Fenner>
re: Can't ID hair like growth in reef aquarium (SMALLER SIZED PICS)     9/6/17

What if I remove the affected rocks couldn't I significantly lessen my biofilter
<? I wouldn't remove the rock permanently... Just to scrub/clean it. B>

Looking for: Lynx Nudibranch’ A.K.A Phidiana lynceus    1/13/14
HELLO FRIENDS. IM HAVING A TERRIBLE TIME WITH HYDROID DIGITA and the lynx nudi is the BEST option THEY CONSUME THESE so I am in need of them I have hundreds of them and they are destroying colonies and other mother colonies. manual removal is not a practical option PLEASE HELP ME. there's a $50.00 finders fee if you can find them . MANY people pointed to you and your team saying that you are the BEST IN THE BUISNESS. thank you
<I/we will post your msg. on WWM; and hold your orig. (this msg.) in reserve... send you anyone's response. Bob Fenner>
re: Lynx Nudibranch’ A.K.A Phidiana lynceus    1/14/14

Thank you Bob and I WILL GIVE you the $50 FINDERS FEE
<No need. I would look over the SeaSlugForum, and our list of marine vendors:
Have your dealer/stockist contact them re. BobF>

Colonial hydroid control - canned air?     3/2/13
Thank you very much for your service, this hobby is full of well-intentioned anecdotal suggestions and assertions. I appreciate being able to communicate with those who are smarter than me about my silly uneducated ideas.
<Glad to help>
I am embarrassed to ask as I do not think my 'original' ideas are ever good ones, but here goes.
I have a 120 gallon reef with coral, fish and about 100lbs or live rock on top of a DSB spilling into a 50 gallon fuge with a DSB and skimmer. I also have colonial hydroids in my tank all over my live rock, shame on me, I invited them in by a period of poor tank maintenance. I have been trying to manually remove them but the porosity of my live rock means they come back; I think I then either need to grind a ton of rock away or learn to live with them as they are relatively deep into my live rock.
<Or take the rock out and let it air-dry for days, weeks>
 If only there were a way to kill the hydroids yet allow the other portions of the live rock to remain alive; if I could only freeze the hydroid tissue without freezing the entire piece of rock. Enter the bad idea; I know about inverting a can of dust-spray and releasing the trigger to release the raw liquid propellant instead of allowing it to create gas when used properly.
As the propellant, to my knowledge, is usually tetrafluoroethane
<http://en.wikipedia.org/wiki/Tetrafluoroethane > or essentially R-134a refrigerant, I deem it to be relatively environmentally safe given that I am only considering spraying a dozen or so spots of embedded hydroids.
Although not good for the environment I am wondering if spraying a dozen or so spots of hydroids on various rocks from reef, rinsing the 'frozen' rock in a bucket of saltwater then reintroducing the rock back into my tank will result in poising the tank (I am assuming that those little hydroid suckers can't survive the freeze)?
<I do think this method is worth trying... outdoors>
Again, I am embarrassed to ask, but I hope that it is less stupid to ask a dumb question than to just go ahead and do it without asking!
<Not a foolish question... Like the many discovered uses of other products (WD-40 comes to mind) you may well have set upon a great idea here. Bob Fenner>

colonial hydroids... Incompatibility, control...     10/30/12
Hello all,
I was hoping you could help me with a problem I am having.
<Will try>
I recently have been fighting colonial hydroids in my tank.
<Can be very trying; VERY persistent>

They have attached to all my live rock. They seem to grow into the rock about 1/2 inch to 2 inches. I have about 90 pounds of live rock in my tank. I have had to pull out all my rock to treat the rock. I have been treating 15-20 pounds at a time. I treat it by using a Dremel to cut off the hydroids
<I'd bleach them... rinse, dechlorinate, air dry>

and the section of rock they are growing from. Next, I use a blow torch to burn the area where I had cut off.

After that I use calk paste and apply it to the area I treated. Following that, I apply epoxy putty.
<Come on!>

After treating the rock I place it in a quarantine tank for several days. If it looks like the rock is clear of hydroids I would place it in the main tank and do the process for another 15 to 20 pounds.
When I was on my last 15 to 20 pounds in quarantine, I noticed hydroids growing on a rock in my display. It was growing out of an area that I actually treated with the blowtorch but didn't calk or cover with epoxy putty. I pulled the rock out burned the area, calked the area, and covered with putty, but I put back in my display because the quarantine still had 20 pounds of rock. After that treatment I had my protein producing excessive amounts of liquid skim for a week 10-12 gallons of liquid skim. Now the skimmer is working fine and the colonial hydroid all seemed gone. Now 3 weeks later I am finding colonial hydroid again. growing out of an area that did not have them before and was not treated. I even found some in my sump on a pieces of ruble rock that was buried in the deep sand bed / mud in the sump.
<Umm, yes>
Any suggestions as to my next method or step I should take?
<Yes; nuking them... bleaching as stated above... using a new ten-fifteen pounds to re-seed the now denuded, dead rock>
I have spent way to much time trying to get rid of colonial hydroids. I am having bad dreams about them.
<I understand>
I would like to start keeping sps corals, but I don't know how the colonial hydroids could influence damage sps corals.
Thanks for your help They look like this picture from the wet web media web site
Tank is 90 gallons, 4 foot long, with 20 gallon sump. It is a fish only live rock tank with the exception of a green star polyps covering about a 2 foot my 3 foot area of the glass of my tank.
<A portion of these can be fragged, re-introduced>
The tank has been running for 6 years. I had not been keeping up to date with water changes, changing bulbs, 2 x 250 watt metal halide. I recently decided to get back to keeping up with water changes, new bulbs, cleaning tank, and checking water: salinity 1.025, ph 8, temp 78, Alk 6, calcium 410, phosphate 0 hard to tell
with test kit, nitrate 0-5 ppm, I am fighting hair algae now I think rock that was burnt may be curing again.
<Press on! Bob Fenner>
Colonial Hydroids from Hades (or some other dark place) coming back from the dead

<Uhh, yes; double-posted. BobF>
colonial hydroids... Incompatibility, control follow up questions  – 12/03/12

colonial hydroids... Incompatibility, control
Hello everyone I hope things are well
<Thank you Jimmy>
I wrote last month about a problem I am having with colonial hydroids. I am taking your advice to bleach rinse and dechlorinate my live rock, if you can point out- or direct me to a link on how to do this procedure-  the best way to do this procedure I would appreciate your direction. 
<Please see here: http://www.wetwebmedia.com/clnornart.htm
and the linked FAQs file above>
I am moving in the next 6 months so  I am not taking out live rock to  "nuke it" right now, but I will take it out when I move.    For now, the hydroid population is small but I can see it growing, so I am not going to battle it just observe the growth.  instead, I acquired some dry live rock, from bulk reef supply, and started curing the rock and I am planning to set up my tank with the new cured rock that was not exposed to the colonial hydroids.
My plan is to be 100% colonial hydroid free.
<In actual practice...>
However I have a few other question: under what conditions can colonial hydroids survive to reproduce or continue living?  
<Most anything solid and wet can transport them>
What can I take from the current system and put into the next?
<W/o bleaching, air-drying... just what you can/do "net">
 Can they survive in a sand bed?
<Not usually, but... possibly... I'd bleach, and/or rinse, sun-dry...>
 Can they survive on my equipment:
<Some can; yes>
 For example, I have a protein skimmer that has a huge colony of feather dusters living in skimmer, can they survive in the skimmer? I have an overflow box, jammed with feather dusters, can they survive reproduce from the overflow? For that matter on any of my pumps, heater, or even on or in my plumbing?  I have been thinking  of my tank like a store going out of business and saying, "EVERY THING MUST GO!!!"  I am trying to get an idea of what that means. 
<Not to be dismissive, or diminish your desires, but I'd not go overboard w/ efforts to eliminate these Hydroids... Unless there of a species,
profusion that is causing real harm... I'd go the moderate route here>
I am planning on keeping my fish, but should I try to collect and keep other organisms from my current set up?
<I would not exclude other organisms>
 Keeping in mind I don't want to take a chance of transferring the hydroids, what could I keep? for example: I have feather dusters, I have some very colorful ones on my live rock and even a few on my sand bed,  can or should I remove some of them?  I have some snails and few crabs can I safely add them to my new system or can the hydroids survive on them or their shells?
<Yes; possibly>
Could I safely harvest copepods from the tank or worms?
I have a large colony of green star polyps can I keep the or safely sell or trade them without spreading the hydroids?
  Some of the green star polyps are attached to live rock some are attached to my glass? and some are attached to my sand bed, what can I keep?   I appreciate your help with this problem.  Thanks again for all that you do here.
<Take some time to think over your plan... I would not go overboard in the effort to eradicate all Hydroid/s directly.
More to be gained, enjoyed by shooting for a mix of desirable life w/ some not so desirable. Bob Fenner>

Can hyposalinity shock kill hydroids in a saltwater tank?    9/3/12
Hi there WWM crew. Hope you all are doing great. I have a 2 gallon dwarf seahorse tank.
<A challenge to keep such small volumes stable, optimized>
I've dealt with hydroids in the past in this tank.
<No fun>
Started all from scratch some months ago. Everything has been good until tonight when I was doing a water change and noticed the free swimming jelly-fish like hydroids. They were like a dozen. I removed all that were visible with a pipette and clean the Aqua Clear filter and its media in fresh RO/DI water. Then I added some freshwater in the little pico tank until it reached 1.017 SG. I did it as a measurement trying to kill the leftover hydroids.
<Hope it works; but I'm doubtful. Also, maybe you'll be lucky and these Hydroids won't turn out to be real trouble. Many species aren't>
I want to know if my attempt may be successful. What I have for life stock is 2 dwarf seahorses, some LR that I cured previously, some Chaeto, media bag of Purigen and 1" of sugar sand. Thanks for any help.
<These organisms are very hard to eliminate.... best to switch out live rock for new... air dry the olde to rid of strobilization. Bob Fenner>

Hydroid Help! 5/16/12
Hi Crew,
as ever, your website is a great source of information and I fear I am re-treading old ground, but I would like to understand what's happening in my tank.
At present, I am setting up a 55gal for seahorses; after it all cycled, I bought some macro-algaes attached to rock to put in the tank, happily added snails after a bit and three peppermint shrimp.  I have since been introduced to the pest that is 'hydroid' in both its forms.  I have removed the piece of rock which has the digitate hydroids, tweezered the things off and torched them where I was able.  I also spotted a small limpet when I was doing this and am hoping it will eat the hydroids in time.
<Mmm, doubtful, unfortunately...>
 Someone said even the shrimp might.  My questions are: 1) how damaging are these critters to seahorses - specifically H. Erectus?
<Mmm, potentially? A big deal>
 2) how long would I have to wait for these things to die off?
<Maybe months>
Or 3) will the jellyfish form breed and create more polyp things?
<May be different organisms... otherwise these polyps should be removed via mechanical filtration in time>
I've attached pictures, as I may have misidentified the critters, but I'm pretty sure they're the dread colonial hydroids and its jelly.
Thanks, Jo
<Welcome Jo... I hope they die off (don't feed, minimally light) the aquarium... take out purposeful life and put elsewhere is what I would do.
Bob Fenner>

Need help with a "bonsai" aquarium... Pest SW Macrophytes and hydroids 8/31/11
I'm in the process of setting up two Fluval Chi aquariums (a small open topped 5 gallon aquarium with a centrally located "splashdown" filter).
<Am familiar; have written reviews re these systems. Very nice in my estimation>
One is a tiny planted freshwater tank which is causing me zero issues and is designed to have lots of green as the central color with blues, golds, whites and light oranges coming from the fish (a small selection of fancy guppies, neon tetras and a Cory). This tank is irrelevant except to show why I'm setting up my "bonsai" saltwater tank in the color scheme and species selection.
<Ah, I see>
On one side is a plant heavy so mainly green colored, freshwater Chi and on the other is a primarily red colored saltwater Chi with an ominous maroon "volcano" rock play land I created by drilling large and small holes in and gluing "volcano" rocks together and dominated by various red macroalgaes.
During normal days there is a halogen desk lamp set up between the two to act as a light source as the Chi has insufficient lighting for plant and macroalgae growth out of the box and is replaced with a Japanese flower vase when entertaining friends.
<Sounds/reads nice>
My freshwater tank has relatively active and frisky small fish. To showcase the contrast, the only finned friend I'm planning on housing in the marine bonsai tank are dwarf seahorses (Hippocampus zosterae).
Although the freshwater tank has been up and running for five months or thereabouts, I have held off on adding the ponies until I felt the tank had appropriately matured.
I currently have everything I plan on adding except the seahorses up and running but recently found two hitchhikers I find troubling. Currently in the tank I have two species of red sea grape (Botryocladia), two species of red Gracilaria, one Nemastoma and one Dragon's Tongue (Halymenia). For cleanup crew and to complete the "bonsai look", I have a number of Nassarius snails, "dwarf Ceriths" of unknown species and wide color morphs sold from a diver in the Florida Keys that will supposedly stay under a half inch (so far the biggest is a quarter inch), one or more species of Asterina starfish plucked from my coral reef, and some random micro brittle starfish removed from the same.
<Mmm, okay... t'were it mine, I'd simply keep physically trimming (while siphoning) the pest/undesired Macrophytes away. BobF>
Need help with a "bonsai" aquarium 8/31/11
I currently have everything I plan on adding except the seahorses up and running but recently found two hitchhikers I find troubling. Currently in the tank I have two species of red sea grape (Botryocladia), two species of red Gracilaria, one Nemastoma and one Dragon's Tongue (Halymenia). For cleanup crew and to complete the "bonsai look", I have a number of Nassarius snails, "dwarf Ceriths" of unknown species and wide color morphs sold from a diver in the Florida Keys that will supposedly stay under a half inch (so far the biggest is a quarter inch), one or more species of Asterina starfish plucked from my coral reef, and some random micro brittle starfish removed from the same. I also have a large number of Opae Ula/Red Volcano Shrimps (Halocaridina rubra) and massive numbers of pods in all shapes and sizes.
The problem and question is this, everything is fat, healthy and breeding so I feel like in general I'm ready for the dwarf seahorses, BUT I have two very active predatory cnidarians of some sort that hitchhiked their way in despite my best efforts at freshwater dips and quarantine time. I know what you really want is a picture, but I've been unable to take one of either creature that does a decent enough job to be better than the verbal description as they are both small and 99% transparent. I assume they are hydroids but do not let that color your interpretation. Either way, they are very active predators of my pods and it scares me about what could happen once I introduce dwarf seahorses and more importantly their food source of BBS/baby brine shrimp.
The first is almost impossibly long for its tiny size, stretching upwards of maybe five inches at maximum. What it looks like is a tiny (about half the size of a bb shot, maybe a quarter) perfectly round transparent ball with tiny tentacles sparsely decorating its entire circumference connected by an incredibly thin but very long tube to my red sea grapes. It can relatively swiftly retract up and down this thin tube in order to hunt down and capture free-swimming small pods. It's really quite fascinating to watch as the "ball" zips up and down with the relatively quick retracting "tube".
The other concern is a hitchhiker that has no other discernible body parts than a similarly thin whip or rope. It is similarly anchored to the macroalgae but rather than having a ball chasing the pods, it stays mostly retracted and when one gets within striking distance (an inch or two at maximum) it whips out at super quick speed to snag the pod. The first is amazing because it's Cnidarian of some sort (I assume) that is stalking and hunting it's prey, the other is fascinating because it must somehow "see" the pods and get triggered out to seize them at an eye blink.
<Do seem like Hydrozoans, Hydroids>
As the BBS are about the same size as the pods these two bizarre creatures are eating, I'm concerned there might be a population explosion (right now there are about six of the first and four of the second that I've found).
Dwarf Seahorse keepers are terrified of just colonial hydroids and now I have two things 100 times more active in their predation. I'm tempted to use Panacur, but that will definitely kill the dwarf Ceriths and probably lots of other beneficial things in the tank. What is your suggestion?
<Remove the infested rock/s and scrub thoroughly w/ a stiff toothbrush, rinse thoroughly in fresh water...>
Add the dwarves and see what happens? Use the Panacur H-bomb? Reboot the tank entirely?
<Remove the Hydroids first. Oh, and read here: http://wetwebmedia.com/marine/inverts/CnidIndex1.htm
Bob Fenner>
Re: Need help with a "bonsai" aquarium 8/31/11

Thank you very much for the advice!
<Certainly welcome. BobF>

hydroids... control 6/29/11
I've had both digitate and colonial hydroids in my 29 gallon mini-reef tank for over a year. The colonial hydroids, especially, have grown over much of the rockwork (see attached pic of Zoanthids/Palythoas engulfed by hydroids).
<Aye yi yi... no fun>
Nutrients are controlled as best as possible (biweekly water changes, limited feeding of livestock), yet the hydroids remain unaffected. Eradication seems impossible without replacing all rock/sand. The hydroids didn't appear during the first year or more that this tank was running. I know they can enter a system via live rock, coral frags, etc., but my question is this: Is any particular type of live rock (for instance, Fiji rock vs. Caribbean/Florida aquacultured rock) more or less likely to harbor these pests?
<Not as far as I'm aware>
Secondly, if an unseen hydroid is somehow attached to a new coral frag or its plug, is there a dip that will kill the hydroid without also impacting the coral, quarantine notwithstanding?
<There is none I know of. Bob Fenner>

Micro-invert ID 6/28/2011
Good afternoon, crew,
I have just recently seen several of these little dudes in my 'fuge. I have searched to the darkest end of the web (may have missed a spot or two), and am clueless. Although I have NO idea what they are, they are fascinating little creatures. The "tail" appendage telescopes from about 5mm to 50mm and retracts again, leading me to believe it is a feeder arm of some sort. The main body is about 2-3 MM in length.
Can you give me a vector, Victor?
<I do think you have a Hydrozoan/Hydropolyp species here... I'd vacuum these out. Stinging if they get into your main system and eating you refugium production where presently encamped. Bob Fenner>

Re: Micro-invert ID 6/28/2011
Thank you. Since my email, I've counted at least 10 so far in my fuge.
Going to be fun getting them all out of my Chaetomorpha!
<Might I suggest a bit of rigid airline tubing attached to the airline as a siphon? BobF>
Re: Micro-invert ID 6/28/2011
Exactly the set-up I used to siphon off the red-brown Planaria that went nuts in my tank earlier. Works very well. I'm a bit more concerned about actually finding all the little freaks hidden in the Chaeto. Maybe remove and rinse it all?
<Worth trying. B>

Hydroid Jellyfish swarming 5/18/11
Hello WWM Crew!
I've a problem that I've been able to identify by looking on your fantastic site, but mine seems no sign of abating.
<Oh oh>
I've a small 6 gallon Fluval EDGE tank (My first Marine tank) that I've converted into a Pico Reef,
<VERY hard to keep such small systems successfully for long>
I've had it running two months, cycled with LR and it's doing wonderfully.
Currently it's stocked with a Briareum Sp. Star Polyp colony, a small green Zoa colony, and a pimply brown Mushie for corals, and livestock is one Yellow Clown Goby, happily feeding on flakes and frozen shrimp, a cleaner shrimp, one Nassarius snail, one Turbo snail and a Dwarf Blue Hermit crab.
I've had no problems with the tank so far in regards to the various baddies that can possibly come in on LR, the tank cycled perfectly and my parameters are spot on. However, from about one month in, I noticed small shapes appearing on my glass, that looking through your site I identified as Hydroid Jellyfish (Staurocladia oahuensis). I spotted the piece of LR that had a few white digitate Hydroid polyps on and gave it a scrub to rid it of them,
but I think the larvae are still multiplying like rabbits. There's some on my glass that I catch now and then with the algae magnet (I have to do this daily), but on the glass portion of my heater, there are literally HUNDREDS of the things.
<Wipe them off, with a paper towel (out of the water, heater unplugged>
I know from looking on your site that these can all appear, and randomly disappear as quickly, but I've had these things in my tank for a month, and with it being so small if it gets worse I fear they might start stinging everything else. Is there any way to remove them safely without damaging any other livestock?
<Mmm, well, at times, yes... a mechanical filter (like a toned down Diatom (tm) can/will filter out the Polypoid forms expediently>
Also, one other question, my green Zoa colony was doing fine, but over the last few days shut up after it 'had a poo', and has only just started to open, but the polyps won't open fully. Is this normal, and will they open fully soon?
<Can't tell from the info. provided. May be "nothing", to some sort of chemical imbalance, allelopathy... You'd do well to scan WWM: http://wetwebmedia.com/mntsmmarsysf6.htm
and the linked files above...>
Thank you in advance,
<Welcome in time. Bob Fenner>

Re: Hydroid Jellyfish swarming 5/18/11
 Hello again Bob/WWM crew!
I thought I'd send on another mail in regards to my small setup, after being pointed to your small aquaria section (Another bit I didn't know existed, thanks Bob!) about running and keeping these things.
As I put before, it's a Fluval EDGE tank with some upgrades, mainly the lighting. It's currently running under two MR16 LEDs, at about 5000k light-wise. This weekend however, I'm changing it to incorporate a TMC Aquabeam 600 LED bar, Reef White colour (Five Cree LEDs in all, three white, two blue). I've also changed the filter media, running filter floss, Polyfilter and some Sera Siporax media balls.
<Good changes, additions>
It's got a Koralia Nano for water movement, directed at the back and towards the surface of the water, so it doesn't blast everything about and helps with aeration, and it's got a Hydor Theo 25w heater.
In my last post I also mentioned the livestock (Currently it's stocked with a Briareium Sp. Star Polyp colony, a small green Zoa colony, and a pimply brown Mushie for corals, and livestock is one Yellow Clown Goby, happily feeding on flakes and frozen shrimp, a cleaner shrimp, one Nassarius snail, one Turbo snail and a Dwarf Blue Hermit crab.) The Goby's been doing well and is eating happily, and both the Cleaner and the Hermit have both molted once.
My query is to what I can do that will improve more quality of life in the system. I knew from doing my research before the tank it would be difficult to look after, but I was prepared to go through with it, as I don't have room for a bigger tank at the moment. As for maintenance, I check the parameters every day, (so far so good) and I perform a 10% water change every week, and any supplemental if I see parameters swing a little. The Goby (after I got him eating) and the Shrimp both seem to be doing fine on flake and frozen/live enriched Brine Shrimp (I'm going to stop the Brine for a while, as it turns out my previously mentioned Hydroid problem thrive on the shrimp)
What do you reckon to the lighting upgrade I have planned?
<Is a good one. Am familiar w/ the TMC LED line... have penned an article re a small sys. w/ these... just last week>
My intention was to get the new lights for coral growth/better life, and then probably try a small hard coral frag (A torch, most likely) and then the last things I'd like to add are probably a few more corals - softies most likely -
<Do take care to "acclimate" all new Cnidarians... I'd place the Euphyllia/s last...>
a small tank-raised clown - obviously provided I make sure I stay on top of everything. I'd just like another opinion on how it might run given time and proper care.
<Could work>
In any case, here's a couple shots of the tank for you, and the Clown Goby hosting the Briareium :)
<Ah, nice>
Thanks for the help, and an awesome site
<The small "squiggly" white spirals evident on the LR behind the Hippolytid Shrimp... these are not what you are/were referring to as Hydroids? They're serpulid/spirorbid worms. BobF>

Myrionema? Nausithoe? I just want it gone!... Scyphozoan contr. 10/6/10
I have several rapidly reproducing colonies of some creature I cannot identify. Each colony member has a flexible tube that it retreats into.
The tube is a clear yellowish color and the mouth of the creature stays very close to the opening of the tube, with about a dozen fluorescent green threads <1/2" long radiating from the mouth. The tubes vary in length but seem to max out at about an inch long (at least in my tank)
<And you suspect...>
What makes me think this is not Myrionema is that it's not brown, and it hasn't stung anything ever that I can tell, it grows side-by-side with corals and I've never had a reason to hate it, except that it's EVERYWHERE and spreading. It's a nuisance just based on it's ability to populate.
<I see>
What makes me not at all believe that this is Nausithoe sp. is that would just simply be too good to be true...and when I get a wild hare and tear out colonies, they appear to sprout back from whatever I wasn't able to remove from the rock. That doesn't sound like any jellyfish I know.
<Mmm, could be>
I've included a link to someone else's picture that looks exactly like what the creature/colony I have in my tank is - I mean to the T. He's got it "identified" but I just can't see how that's right.
Good news would be appreciated, but I'm ready for the worst.
Here's the pic:
<Mmm, well... this pic does seem to be of Nausithoe racemosa... I don't know re control, specific predators... at the worst, you may have to remove, break off all wanted life, nuke (bleach...) the rock... start with some new... Bob Fenner>
Thanks in advance!

Dear WWM crew,
<Hi there Bill>
Lately I've been seeing these little things in my tank, mostly on my refugium (in the sponge) see pic below
They look almost transparent and if you magnify the pic 200%, you'll see that they are kind of spiny (3rd pic).
I was told that they are DIGITATE HYDROIDS, is that correct?
<Might well be>:
Are these things harmful to fish?
<Mmm, well, they can be... in large numbers...>
I have no corals in my tank, just a FOWLR tank.
If so, how can I get rid of them? My tank is in it's 4th week of going fallow.
<Most often such organisms are "transitional" in new set-ups... in other words, they most often "go" of their own accord. I would not do anything overt at this juncture. Please read here for more:
and the linked files above. Bob Fenner>

Invertebrates... Hydrozoan (?) control, hermit crab parasite/symbiont? 7/2/10
What's up? I love the site.
<Well okay!>
I have a question about something in my tank... I got about a pound of LR a few days after I set up my tank and I noticed this stuff on one of the small rocks; it looked like maybe a "hair algae" to me - I hadn't done any research about algae or LR at this point. I didn't think anything of it.
When I got my 2 blue-legged & 1 red-legged hermits the red-legged hermit ate it off the rock. It's pom-pom-shaped and each "strip?" has a tip like a "Hydrozoan." Which each move independently, so I know it isn't an algae, but some kind of animal. The thing is they're multiplying all over the panes of glass where the red-legged hermit can't get to them. Now after getting a tiny hint of info I've scraped them off the glass and tried sucking out as much of them as I can with a turkey baster, but is there anything else that will eat them? ...off the glass.
<Not likely, no. You may have some "luck" with time going by... their dying off for whatever reason/s. Read here:
Also, I'd like to know some advice about a boring worm in my red-legged hermit crab.. there are two, one smaller than the other. Should I try to extract them? Can you tell me how?
<Maybe, with tweezers...>
I haven't been able to find much info on the net at all, except that they eat hermit crab eggs. It's supposedly a symbiosi? How do the hermit crabs benefit from them?
<Sounds more like space "parasites"... in some classification schemes for Symbioses, there are classes of parasitism... where the symbiont gains at the expense of their hosts... Bob Fenner>

Hydroid Myrionema 01/20/09 Hi Crew, <Aloha Clay> I have a problem with what I believe are hydroids (myrionema) and would like to get your advice. The photos that I have seen online appear to match what is in my 90 gallon reef tank. There are 4 or 5 small patches on a large rock that is a little larger than a football. The rock is located on top of 2 equally large rocks forming a cave so it would be easy to pull. I have not observed the hydroids on any other rock. From research on your site and others, the options for controlling or killing these are not great. Since the rock is easily removed, should I just pull the rock from the tank to prevent further spread? <This is one option. But it's an extreme one. If it were me, I would take the rock out and use a Dremel saw (or a screw driver and a hammer) to chisel off the parts of the rock with the hydroids. Then rinse the rock off very well with salt water (preferably from your tank-- you could even do a water change at the same time). You can't just scrub them off or else they'll grow back. And if you don't rinse the rock really well, some fragments of the hydroids might remain and grow back.> I have 2 nice leathers attached to it that I can frag and salvage. However, there is very nice GSP colony that I fear will be lost since one of the hydroid colonies has begun to overgrow it. If I remove the rock, what damage will this do to my biological filtration? The rock represents probably 15-20 percent of my total rock. The tank is 1.5 years old and I haven't added anything for 6 months so I am not sure how they got into the tank. Can these creatures lie dormant in the rock for long periods? Any advice you can provide would be greatly appreciated. <Do try the method described above-- might spare your rock and your corals. ;-)> Thanks, Clay <De nada, Sara M.>

Digitate Hydroids. Danger? Control? 11/29/08 Hello WWM Crew. I recently added some Live Rock into my tank and noticed that i have a few Digitate Hydroids. I have searched the internet to find out about them and i have read that these give a nasty sting to corals. <That's not always true. It depends on the type of coral and the type of hydroids. Some hydroids are harmless.> Several other websites have advised to get rid of these as soon as possible, several different methods have been mentioned, including Kalkwasser Paste, Injecting with Vinegar. The problem i have is that the piece of Live Rock they are on is full of Polyps and i do not want to kill these. <Are you sure the hydroids are stinging your coral? You should be able to see signs of this on the corals. It will look as if they've been "burned" or they will be closed up around the hydroids. If you don't notice any obvious signs that the hydroids are stinging the coral, I wouldn't risk doing more harm than good by trying to kill them.> Some other sites have said that these creatures thrive on high nitrates and phosphates and therefore when my tank has gone through the cycle that these will just die, is this true? <This is a possibility. In any case, theses kinds of animals usually come in waves and will likely die off on their own eventually.> I can't seem to find much information on these, if they are so bad, surely there would be more information out there?. <I wouldn't worry about them unless you can see that they're doing damage.> Thank you for taking the time to read this, and any help or advice will be appreciated. Kind Regards Jo <De nada, Sara M.>

Re: Digitate Hydroids attn Sara 12/02/08 Thank you kindly for your response. 12/01/08 The only reason i noticed the hydroids is because the polyps were all shriveled and grey and never opened, <Oh, that's no good.> which makes me think that these hydroids have killed them. I don't really know what to do next, I have been told that the hydroids can multiply and take over. I am not sure about adding any corals now, as I do not want to kill them. <Unfortunately, if the hydroids are growing right up against your corals, I don't know what you could do to kill them that wouldn't also hurt the coral. What kind of polyps are the coral? If they are soft corals, you could try removing the coral from the rock...> Any advice would be appreciated <Reducing nutrients and pollutants in your system is always a good thing... so if there are ways you can do this, it can't hurt.> Thanks Jo <Best, Sara M.>

Hydroids: growing problem..., control 11/29/08 Hi there! I am about to give up my fight against brown hydroids. Read some nice article on how to kill them with calcium hydroxide paste (Kalk) but it doesn't work. Tried brushing and even crushing a layer of LR surface (a few millimeters at least) with coral cutters. Nothing works. <One "last" thing you can try is NaOH mixed with Kalk. See here: http://www.asira.org/killingaiptasiaxeniaetc > They seem to borrow in the rock and retract several millimeters within the LR. I read that Berghia Nudibranch are useless against them. I also just read that limpets, and possibly keyhole limpets in particular, could eat them. Is it really worth a try? <I don't see why not. I'd try to get as many as possible of them with the NaOH... then maybe see if the limpets can help keep them from coming back.> What specific limpet species should I use to try eradicate the brown hydroids? <I honestly don't know... but these critters will vary from individual to individual (not merely from species to species). I would suggest you ask Morgan Lidster at Inland aquatics. If anyone would know, he would. http://www.inlandaquatics.com/> Otherwise the only other option I see is changing all my LR, but that is quite an expense and a lot of trouble and in the end there could be a few left somewhere under a coral (even as a medusa...). <Oh no... don't do that! Try these other things first. If all else fails, I suggest giving up. Seriously, in my experience, sometimes giving up sometimes works eventually. ;-)> Thanks for your advice! Dominique <Best, Sara M.>

Re: Hydroids: growing problem... 11/29/08 Thanks a lot for the NaOH tip. Will try it soon (will talk to the pharmacist -who knows- otherwise will order from Fisher sc.). <Oh, no need to speak to a pharmacist... just look for "Red Devil" drain cleaner... it is, more or less, pure NaOH. I get mine on eBay. http://shop.ebay.com/_W0QQ_nkwZredQ20devilQ20lye Just... again, as the site says, be VERY careful with it. It DOES burn.> Very interesting site too Asira.com, didn't know it. <Thanks... is my own personal creation. ;-)> And for the limpets I already sent an e-mail to Morgan Lidster. <Ah, good... he is one of the "best kept secrets" in our hobby... likely more knowledgeable than any of us here, save Mr. Fenner. But unfortunately, he is a bit of a recluse. If you ever go to a MACNA, I highly suggest you seek him out... just be sure to carry a good bottle scotch with you (his weakness apparently).><<Heeeee! You DO know Morg! RMF>> Thanks again! Dominique <De nada, Sara M.>

Re: Hydroids: growing problem... 12/03/08 Hi! Does Sodium hydroxide precipitate Phosphate (like Calcium hydroxide [Kalk] does)? <Good question... I imagine that it does to some extent and for some phosphate. But I certainly wouldn't use it for that.> Thanks! <Best,
Sara M.>

Hydroid, ID, control... 11/14/08 Hello all! <Mariusz> I was hoping you could give me an ID (ie. scientific/common name) on this Hydroid. It was taken from: http://www.wetwebmedia.com/hyzoanidfaq.htm (i have also attached the same pic). I have a bunch of these in 120 tank with about 140lbs of live rock. <Mmmm... can't tell the species from this small pic> I recently took all fish out of the tank to let run fallow after a parasitic infest. Most corals have been removed (for other reasons). All that is left are a few mushrooms and leathers, peppermint shrimp, hermits. The tank has been running fallow for 6 weeks now and I'm in no rush to put my livestock back in. Also for 6 weeks I haven't put any food in the tank either, it's just been running with Deltec skimmer (which hasn't produced much as I have almost no livestock and no feeding). So questions: 1) are these hydroids a danger to fish? not sure how potent the sting is. <Could be... if they're unaware, get too much exposure> 2) How can I rid these with out manual removal as I've been trying for almost a year. Not sure if these guys are worms of some sort and if de-wormer will work, possibly Prazi or other. Is there any biological alternative? Without proper ID its been difficult moving forward towards a solution. Thanks <Can be very difficult... frustrating up to the point, extreme, of making it reasonable to bleach/kill all LR, start over with some new LR material placed over, amongst, using the killed rock as base... Otherwise, you might be lucky to discover a predator (perhaps an Opistobranch...), but even here, they wouldn't eliminate all... "So many chickens, so many foxes"... Bob Fenner, who would bleach, nuke>

Re: Specific tank questions... Hydroid contr. -- 07/14/08 What would a LFS do with the rock with hydroids? Just wondering. Matthew Harless <Mmm, a few approaches to control... nutrient limitation, predation, poisons... Read here: http://wetwebmedia.com/hyzoancompfaq.htm BobF>

Re: Specific tank questions I'm sorry I meant why would they want to take them from me? You suggested that I sell/trade the hydroid infested rock to a dealer and I was just curious why they would want it. Not an important question, I was just curious. Matthew Harless <Mmm, that profit motive thing... "One persons noisome Mushrooms is another persons income"...the future belongs to commerce. B> Re: Specific tank questions I misunderstood. I thought you meant to sell them the brown hydroids (myrionema), but you were talking about the Corallimorphs. Thanks for the clarification. Matthew Harless <Ahh! Thank you. B>

Hydroids, control -- 6/4/08 Hello again Crew, <Hello> After a hair algae explosion, I now have an explosion of hydroids (see pic below). <No picture attached'¦> They are covering all of the surfaces inside the aquarium and sump. I don't mind them because they are simply demonstrating the "fertility" of my aquarium. <Rather the polluted state. Plague levels of a single organism are never signs of a healthy ecosystem; biodiversity is the key.> They're very small, so should I be worried about them stinging? <Yes. Many hydroids pack a wallop.> Will my snails and/or hermit crabs eat them and/or the hair algae? <No. Careful control of nutrient, overfeeding, etc. will thin the herd.> Well, I have to catch the bus. Thanks in Advance, <Welcome> Random Aquarist <Specific Benjamin>

Help with Hydroid myrionema. - 04/14/08 Hello Again. I believer you are correct on what i have (hydroid myrionema). We have a hard time getting rid of it. <Yes... can be a real bugger> I have searched on line for remedies. With my tank being 200 gal. reef safe with the following (blue tang/unicorn tang/clown tang/2 yellow tangs/cleaner wrasse/Lunare wrasse/blue damsel/Banggai cardinal/pajama cardinal/blood red Hawkfish and a mated pair of green mandarin gobies) a clean up crew and we have feather dusters/tube anemones/polyps/frogspawn/leather corral and mushrooms. We do water changes for nitrate levels, and have decided to move to the Zeo system. However i wanted to know what this Panacur is all about. On line people have used it to get rid of the hydroids, but does it work, and will it help me. Thanks MC <Mmmm, what are the active ingredients in this product? Bob Fenner.

Re: Help with Hydroid myrionema. 4/16/08 April 15, 2008 Hi again. I'm sorry the product people are using to get rid of Hydroid Myrionema is Panacur, the main active ingredients is Fenbendazole. <Ahh!> I wanted to know if i could use it? <Mmm, well... it may well kill off a good deal of the "wormy" life in the system... is an anthelmintic... and most all marine systems, natural and aquarium have substantial worm faunas... So, at the least I'd have a good deal of pre-made water ready, be aware that changes may need to be made... successively, along with the use of chemical filtrants, change of mechanical media, cleaning of skimmer/s...> But I wanted to make sure i don't kill off my tank. <You are wise here> What do you suggest? I'm at my wits end with this hydroid, (working on it for over 9 months) and if it weren't for my mated pair of green mandarin gobies, which are doing very well, i would kill of my rock and start over. <Mmm... I would try some biological controls first myself... or move all the "desired" livestock elsewhere for a few weeks, while using the "de-wormer". BobF>

Hydroid jellyfish -01/29/2008 Hi, I have a lot of these in my tank glass. I try to use the magnet cleaner to scrape these off, but their number never seems to reduce. Is there a way to remove these from the tank? Thanks in advance. <Patience and time work best. These things typically have population boom and bust cycles. You can help things along by scraping them off with a razor blade (if a glass tank), and suck them up with a water change.> Regards, Kash <Best,

Hydro ID and help -- 1/04/08 Hi guys, Thanks for maintaining such a wonderful site. I have been visiting this site for over 4 years now and have always found to be a great source of information. I need a little help though, and would appreciate it if you guys could give me a hand. <Will gladly render my input> I'm looking for a positive ID on this little critter (see attached). After exhausting all resources here at WWM on Hydrozoans, I went looking for better classifications of these guys and I found a great site for identification: http://www.ville-ge.ch/mhng/hydrozoa/hydrozoa-directory.htm. I think I've come to the conclusion that this is probably Class Hydrozoa, Order leptomedusae Family Malagazziidae <Appears so to me as well> I only see them in the Hydroid colony stage. Hopefully I'll never see the medusa stage ;) <Is, will be there in time... likely being removed by your mechanical filtration> Anyhow, looking through the articles at WWM I'm trying to find out how to really get rid of these guys. Everything I've seen at WWM says starve them out and remove the nutrient rich environment. My question then becomes "what nutrients?" <In boldest statement of what can be easily measured, soluble nitrate, phosphate...> What do these guys depend on to grow? <Mmm... some chemical base, micro-fauna... a dearth of predators, competitors> Although, the appearance of these things seem to correlate with my use of Koralle-VM from Brightwell Aquatics. I have since changed to Coral-Vital from Marc Weiss Companies, Inc to see if it will have a different effect. <I would drop this Weiss product... and most all of its ilk> They also seem to be accompanied by this brown looking mush on the live rock. I have an 11 Gal Aqua-via tank, with an Aqua C remora Protein skimmer with Maxi Jet 1200, 25lbs LR and a 3in sand bed. I only have a couple of zoo's and a single clown fish. Not really much of a bio-load here. The Aqua C should be more than enough of a protein skimmer for this tank/load. Any ideas on how to starve these guys out? Any specifics would be greatly appreciated. Thanks, Jas <Mmm... well... I might try a small shrimp (or two)... perhaps Lysmata wurdemanni... in the hopes of them eating up the hydroids. Bob Fenner>

Digitate Hydroids, contr. 10/3/07 I have 20+ Digitate Hydroids in my 29 gallon reef tank. The population is getting to a point where the numbers are starting to worry me. I've had a population explosion of them over the past month. Most disturbing is that this month has been the most solid on husbandry for the tank as well. The tank is about 6 months old, has weekly 20% water changes and is skimmed fairly heavily. They are really a concern because I have had corals affected by them, and have actually had some tissue loss due to the them as well. <Not good> Manual removal is extremely difficult for most because of placement. Kalkwasser injection is also very difficult because some of these guys are really small. I've superglued over them; used tweezers on them; attempted to Kalk smother them. I've dealt with pests, but I'm completely at a loss at ridding the tank of these guys. Searching the internet high and low I have found little in the way of tried and true recommendations. I've read the population can wane with nutrient control, but in no way do I consider my tank nutrient rich. Do they have a natural predator? <A few... but these can be very species specific...> Is there a treatment? <Mmm, not ones that are very satisfying... removing the rock... letting it dry... to kill off...> I'm worried that if I don't get this under control and the population continues growing that I may need to start at square one again. Regards, Jarred in Portland, OR <A pic please (close-up, well-resolved)... and where did the rock originate (which sea, island group?)... Bob Fenner>

Re: Digitate Hydroids, contr. 1/20/08 Unfortunately, I'm not sure where the rock is from. Somewhere in the Pacific I believe. <Okay> Attached the best picture I could get of one of the digitate hydroids. This one is dead, but when alive they look thread-like like most of the pictures you'd see on the net. Thank you! <Mmm, I would try removing all these... manually... take the rock out, systematically scrub, scrape all off at the base... rinse... replace the rock in the tank. Hope. Bob Fenner>

Stinging Hydroids HELP w/ pred. control - 4/7/07 Once again I'm back for expert advice.. <Okay> I've done some extensive reading on stinging hydroids on your site. In fact, I've found my pests picture here http://www.wetwebmedia.com/hyzoanidfaq.htm Article: Bad boyz- hydroids 12/30/03 You've mentioned in other articles that these have few reef safe predators. <Yes... though these are often quite "species specific"> What would the predators be of the "tube like coiled at the base" string hydroids ? Nudibranch is one critter that keeps coming up. <Some species... definitely not many/all> I have sooo many at this point, scraping them off would take forever. Thanks, Chris <Well... the path may be long here... and not one I would take... experimenting blindly... If you want to go this predator route, FIRST (dang, that's bright), you should determine as closely as practical, which species of Hydroid you have... will require the use of reference works, a microscope likely... I'd try writing some folks on the Net who work in the field of taxonomy, biology of the Hydrozoans for suggestions here... Bob Fenner>

Re: Starfish and Hydroids? Blue Linckia (Linckia laevigata) Better Left in the Sea. 2/9/07 <Hello again Travis!> Thanks for the great info, Mich! I'll avoid the blue Linckia star! <Very good!> Follow-up question: <Sure.> Would any/all starfish be damaged/irritated by crawling over rocks covered in hydroids? <Yes, it is possible.> i.e. If my rocks are mostly covered in hydroids, do I have to rid my tank of them before I could add any (non-sand-dwelling) starfish? <Mmm, no, but again not for the reasons you state. I am hesitant to recommend any starfish that are of the "rock scrubbing" type which I believe you are considering. Most just don't do well. Serpent and brittle stars should be fine. I wouldn't recommend the sand sifting star either, as it will take out much of the beneficial fauna in the sand bed and then starve. Hope that helps! -Mich> Travis. Hydroid control? 1/27/07 Hello...this is Stephanie. <Hi, Stephanie! GrahamT here.> I am new to nano reefing. <Welcome to the world of micro.> I have been reading about hydroid problems with zooanthids, unfortunately, we were too late in saving it. It smelled pretty bad and didn't look to good. <Unfortunate... sorry for that.> But, my question....could this problem have spread to our hairy mushroom? <If you mean, can it spread nearby and sting, yep. If you mean can it infest the mushroom, then I have to say I'm not familiar with them moving about. I am somewhat inexperienced in the hydroid "field" but in my research ( http://www.wetwebmedia.com/hydrozoans.htm and all links...)I learned that they need somewhat higher concentrations of nutrient to thrive. Also, they are usually "fixed" to the rock.> It looks good but has a few areas that look similar to the zoanthid. <Am I missing a past email? What did the Zoo look like?> Please help..... <Trying... -GrahamT>

Hydroid control? <follow-up> 1/28/07 Thank you for the quick response, Graham T. <Welcome, though not immensely helpful, I suppose.> I made an error when I put Zoanthid, I should have put hydroid. The patch on the mushroom, or I should say on the rock is grayish and looks velvety. The other spot on the Zoo was actually "moving" little things you could barely see. So, somewhat different but I am worried I will miss this and then it will be too late. <I want to be sure not to mis-diagnose. Is there a chance you could send a pic (under 400K) so I can get a look at the critter?> OR.....could this be fungus? The rest of my life rock doesn't show any areas like this one. Overreacting or playing it safe? <Always playing it safe... -GrahamT.> Thanks Steph

Hydroids infesting my Zoanthids? Dear Crew, <Russell> Here's a new one for me...maybe you also? <Could be> Over the holidays my Zoa's (four frags, about six months old and previously healthy) closed up and became infested with little critters. My Ca and dKH dipped mildly when I was out of town for three days, but otherwise the tank was stable.. (need to get a calcium reactor, my 2-part dosing pump is temperamental). These parasite-like things attach to the closed polyps and are too small to photograph accurately. They look like a small (1-3mm) hydroid-ish creatures, having a clear stalk with small white-brown tentacles. They start like white little dots and grow pretty fast, spreading to all colonies and show tiny tentacles. I had hydroids on my tank walls last year, but they went away after a month or so. <Typical> Last week I removed the frags (some had already grown on to surrounding rocks) and did a 15 minute dip in a gallon of tank water with a salinity of 1.015 and over a tablespoon of Lugol's... at the same time blasting the frags with a turkey baster. This seemed to do the trick upon reintroduction... most polyps re-opening and looking good. <Good> Then, over the last two days, the little critters came back so last night I re-dipped the frags- same as above except for 30 minutes AND I followed this with a flash RO/DI water dip. I also pruned and discarded the remaining small amount of new growth- polyps left behind on my LR (figuring these small stragglers were still infected and causing the problem). <Mmm... much more likely to be residual animals in your system... really need to dip, move the Zoanthids to another setting> This morning the frags, for the most part, are open with no obvious critters. Could these be hydroids?? <Oh yes> I've searched this site (and others) and am confident it is not "reef pox" which is more pustular, ulcerative in nature. If these apparent parasites come back, any other ideas???? <Mmm, plenty> Interestingly, I also recently picked three Nudibranchs off the Zoa frags. I don't think the infestation is from Nudi eggs. Also, they are not Zoa spiders. Thanks, Russell in KY <Hopefully gone for good this time. Bob Fenner>

- Choerodon fasciata & little stinging hydroids - Dear WWM Crew, I have a 240 Gallon with approximately 70 pounds live rock. On 11-22-02 I added a Harlequin Tuskfish "Tigger" that had been quarantined for two weeks with no signs of parasites or other. I have noticed tiny Hydroid jellyfish (polyps) on the glass (dots with legs). At first I thought this was a really cool find from the live rock, but a few days ago I noticed spots on the pectoral and tail fin of Tigger, on closer inspection these spots really appear to be the Hydroid polyps. Can these polyps attack the fish and be a parasite of sorts? <Not attack, per se... but if the fish bumps up against them... sure. But I will just add, as I also have a harlequin tusk, that spots on the tail are not uncommon. They come and go pretty regularly.> Tigger's color is bright and is eating well, and does not appear to be scratching or have any abnormal breathing. <Good deal.> There are not any other fish in the tank. I am concerned about Tigger's health, the health of the tank, and about adding any new fish until I am sure these hydroid polyps are not going to cause a problem. <No fun... you may want to consider creating a scraper/siphon combination that would allow you to scape off a hydroid and immediately suck it out of the tank. You definitely don't want these floating around the tank. You may need to take more drastic action, I'm sorry to say. Hydroids are a pain - quite literally.> Your help is greatly appreciated!! Thank You. Jen Marshall <Cheers, J -- >

Removing finger-like hydroids Stinging hydroids have few natural predators that we can regard as reef-safe. If you have corals in the tank, it may be difficult to avoid manual extraction. In the meantime, you could try a stiff bristled toothbrush tied to the end of a siphon tube so that you could siphon slowly and scrub at the same time. We need to avoid fragmenting and spreading them. Bets regards, Anthony>

- Hydroid Problems - Hello. <Hello, JasonC here.> How are you today? <Well, thanks for asking.> I have a 55gal. tank set-up for a little over a year with a sebae, two clown perculas, Zoanthid, a hairy mushroom, Sarcophyton, electric star polyps, various sponges (blue, red candy cane, and yellow), a green hard coral, 3 crabs, 8 snails, and a velvet damsel. I have PC lighting 6-65watts, new bulbs every six months whether they need it or not, CPR Bak Pak II protein skimmer and a calcium reactor. All have lived happy and healthy in this environment. About three months ago a friend bought me a sun coral. I quarantined it for three weeks to ensure it was eating correctly and content. I added the coral and three to four weeks later I noticed a lot of "feathers" in the tank on all of the live rock. I am positive it has been identified on your site... hydroids. <Egads.> I tried the siphoning technique but the base is so far into the crevices it reproduced 10 fold. My question is how bad can these things affect my tank? <Well... for their size, they are pretty potent stingers.> I am afraid they are affecting my Sebae. <Quite possible.> He is sitting up but he is not taking the food the perculas bring him. His mouth is open slightly. I feel that if the anemone dies, the perculas will die also. <Not so, they will be fine.> I have to save them! <No worries.> I assume the problem is the hydroids because the sun coral is non toxic. <All corals have the ability to wage chemical warfare.> I have not used any chemicals in the tank since it was formed. I tested the water: 440 ppm calcium, NH 0, pH 8.1 alk Normal, NO3 0, NO2 .05. I am sure the NO2 are just a cycle. What can I do to get rid of the hydroids short of finding a sea dragon, Pteraeolidia ianthina. <Not really that east due to their size - you may have to extract the rocks they are on and remove the hydroids with tweezers.> I have not found a single supplier of them. <The sea dragon? Heavens no... these typically do very poorly in captivity.> If you can think of a single other reason for the eating habits of the Sebae please I am open for suggestions. <Consider more lighting.> My Sebae was a tank split and my tank mimics the conditions it was raised under. <Lighting as well? Most all anemones need intense lighting, and yours is likely not intense enough.> Please help. --Hydroid Hater-Tonia <Cheers, J -- >

Threaded Hydroid? 6/12/04 No emergency here, just trying to better understand my tank. I have a nice, healthy Devils Hand (Lobophytum) that at night puts out one or two relatively long (up to 7 inches) thin fibers that have "off-shoots" about a quarter inch long spaced at regular intervals. It looks like a tank sized long line fishing rig. <yikes... this is not actually part of the leather coral, although it looks like it. I have a strong suspicion here. One of the threaded hydroids. Does this thing look like a barely discernable wisp of a thread... and the "branches" like teeth on a sparse/coarse comb?> The fibers come out of one of the yellow fingers. Is it trying to feed or is it a defense mechanism. If the latter, should I avoid placing another coral within its reach? <yes regardless... keep all other critters away. And if its a hydroid, watch your arm too... a nasty sting is possible> Many thanks. Your site has made a material contribution to my 38 gallon reef's growing success. <no worries my friend... if this is a hydroid, it can be removed (and future ones can/should be screened by running all new livestock faithfully through a proper 4 week QT). Anthony>

Threaded Hydroid? II 6/12/04 Many thank you for the id Anthony. I am not worthy of such expert advice. <we are all on equal footing here my friend... as aquarists we each have our specialties, and we all evolve in time> I only found one picture on the web that looks like it, the "sparse comb" you so aptly describe. How shall I remove it? How about cutting off the finger it emerges from? <no need to cut the leather, just look at the base and see if you can see ho well it is anchored (often appearing like a transparent fleshy plate/base in the case of this type)> Will it move around the tank if I leave it? <not too motile> After just 8 months with the reef, I am clearly in new territory here... Dan <its all a learning process... no worries. Enjoy the journey. Anthony> Stinging hydroids 6/15/04 Hi Guys <cheers> Wonder if you can help me. Are there any species of fish or invertebrate which would feed on stinging hydroids? I'm having difficulty controlling them in my tank. Thanks and regards Adrian <while there are many fishes and invertebrates that will control hydroids... they are not likely to safe with your other fishes and/or invertebrates (cnidarian feeding Chaetodontids, Asteroid sea stars, etc.). And if you could ID your species of hydroid and find a nudibranch, for example, that was an obligate predator... the nudibranch would soon starve. Your real solution is to get to the root of the problem (excess nutrients) and not focus on the symptom (hydroids flaring). Focus on starving them into submission and then polishing them off with a lite bit of manual control. Improve water changes, be more aggressive about skimming, increase water flow to get excess food/particulates exported rather than lingering to feed the hydroids, etc. Best of luck! Anthony>

Digitated Hydroids Good afternoon crew, <Good day> I posed a question on the forums last week, and no one really had an answer for me. The only suggestion I got, was to email you all and see if you had any good info to share with me. Thank you for any assistance you may provide. Here is the original post from the Marine Invertebrate forum: Here is the situation: I currently have 5 of these nasty hydroids (digitated hydroids). Two of them extend to 4in. at night, two of them extend to 3in., and one of them to about an 1 1/2 inches. Of these five, I can reach 3 of them (one large, one medium and the small sized one). The other two are nestled deep into the back of my largest live rock, and there is no way I can get to them. Even if I was able to move all other LR and creatures off of it, they are in deep crevices that are barely wide enough to stick a nail in. Here is my question (which you could probably guess.. hehe): Does anyone have good experience with removing these type of hydroids? If so, what was your method? Also, I have had different hydroids in the past, not many but a few, and they generally cycled out within a couple weeks to a month. If you have had them before (the digitated kind), how long did it take for them to cycle out? I wouldn't even mind letting them just do that, except a few of them are getting way to close to some of my corals at night, when they extend themselves. Current setup: 100g 30g sump/fuge (LV, 4in. LS, macro algae) AquaC EV180 12x turnover Magnum 350 canister (changed weekly with carbon) 100lb LV Test readings: NH3/NH4, NO2, NO3 = 0 pH = 8.3 Temp = 78 to 80 Ca = 400 ALK = 9 dKH sg = 1.024 Kent sea salt, 10 to 15% weekly water change, no additives <Erica, if it were me, I would get a syringe from the pharmacy and make up a strong solution of Kalkwasser and when the buggers are out, inject them with that. It should do the trick. James (Salty Dog)>

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