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>

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:
http://www.masa.asn.au/phpBB3/viewtopic.php?f=53&t=221761
<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!
Red

Hitchhiking Medusae - 10/14/06 Crew, thanks for all your help in the past, you are the best. <<Happy you think so <grin> >> So I have what appear to be some medusa-like, free-swimming discs, about ¼' maximum in size with 10-14 tentacles that have popped up and started swimming around. <<Hmm, some hitchhiking jellyfish maybe (Cassiopeia sp.)? They pulse around the tank and either attach to the glass, rock or coral, or worse I siphoned 5 off of my bipinnata (my favorite coral). <<On your gorgonian eh...as noxious as these are I doubt they were doing any more than resting>> As they are free swimmers this is new to me, it seems that a red-legged hermit won't do the job. <<Why do you assume these are a "bad" thing?  Either way, it is likely they will pass as quickly as they appeared>> I'm loath to add a butterfly fish as I have so much coral.  Should I try Lysmata wurdemanni? <<I think you need to identify or ascertain whether or not these medusae are a threat...else just enjoy them while they are present>> I have 2 cleaner shrimp in the tank, a Foxface, hippo tang, orchid Dottyback, and 2 clowns.  It's a 75G display with 55G sump, so I have no load problems and change water regularly. <<Mmm...ultimately too small for the Hippo tang in my opinion>>   They look sort of like: http://www.wetwebmedia.com/Cnidarians/bugs.jpeg Or http://www.wetwebmedia.com/Cnidarians/Anthozoans/AnemonePIX/Anemone_10X.jpg http://www.wetwebmedia.com/Cnidarians/Anthozoans/AnemonePIX/Anemone2060.jpg Are they the "early" stage of a glass anemone and they are just waiting to turn into polyps? <<I don't believe so, no>> They aren't in plague proportions but I see them swimming around every time I look at the tank.  Thoughts, or like most pests should I just wait for it to pass? <<You make no mention of any deleterious effects from these newcomers...I would simply enjoy them for what they are as I truly expect they will "pass">> All the best, Marc Weiser <<Regards, Eric Russell>>

Re: Hitchhiking Medusae - 10/17/06 Thanks for the response. <<Quite welcome>> I agree on the Hippo Tang, bad advice early on.  The wife thinks it should even go! <<Ah, yes!  These fish are quite susceptible to developmental retardation when kept/grown-up in too small quarters>> On my "swimmers" I'll watch.  The corals don't seem to be reacting negatively, anything I should be watching for? <<Just that, negative reactions...but likely not a concern as previously stated.  Cheers, Eric Russell>>

Upside down jellyfish 9/8/04 Hello. <howdy> I have been planning on making a clam tank and have been designing it for over a month. then I saw an article talking about the upside down jelly fish. and I admit it, I want one. The tank it would go into will be shallow with a wide bottom, gentle current flow, and bright lights. the only problem is, according to the article, they secrete their stinging cells in their mucus, and it can kill other animals in the tank. <they really do best in a species tank.  muddy lagoonal set up would be nice. Do consider some Thalassia sea grasses too for the biotope> my question is, are clams vulnerable to the stinging of the upside down jelly fish? <they would be a very unnatural combination and the clams might easily outcompete the jellies as filter feeders. Not recommended. Please do consider setting up a natural display> No dolphins were harmed in the making of this email.  I did have to kill a few baby seals though. <ahhh... OK, Club Happy in Boise. Just Happy in Pgh - Anthony :)> Jellyfish I was looking into my tank at my new Blue Linckia Starfish (thank you for the advice by the way, he's doing great!) and I saw a tiny (about 1mm) jellyfish swimming around my clownfish, it must have come in with my live rock. I could tell that it is a jellyfish because of the way it was moving; it's really quite unmistakable. What should I do with it? Will it harm my fish?  Do you have any idea how large it will get? If I decide to get rid of it what can I do with it, I don't want to kill it.  Thanks, Elizabeth  <Liz, jellyfish are not reef safe and most are toxic to people. Take it back to the store and see if they want it. I don't believe you would want to set up a small tank for it and furnish it the necessary plankton it needs to survive at this stage. James (Salty Dog)><<Uhh, one millimeter... just ignore it... they too shall pass. RMF>>

Pteraeolidia ianthina availability... Hydroid control  11/13/05 Need to purchase Pteraeolidia ianthina to control nuisance hydroid in my 125 gal reef tank. Can you advise? Thank you. Pat Boss Breezy Point Resort http://www.breezypointresortozarks.com/  <Mmm, take the last "i" out of the species name and send your request to the seaslugforum.net and to wholesalers (via your LFS and online marine livestock wholesalers like Fosters & Smith, Marine Depot... and hope. Common in the P.I., not in the trade. I'd be looking for other control possibilities. Bob Fenner> 

Re: Hydroid eating nudibranch  11/14/05 Mr. Fenner, I apologize for any misspellings, but I got my information from the Julian Sprung Invertebrates book and I doubled checked the spelling and it is correct per his book on page 98. <Mmm, no worries... just thought you might want to know of the other spelling... for checking purposes> For my lack of knowledge and really wanting to correct this problem, please help me find another solution. I live at Lake of the Ozarks in Missouri in a remote area and would really appreciate your expertise. Please respond. Deb Brayton, a wanna be great aquarist. <Mmm, have you read much re hydroids? Know the species or genus you believe to be dealing with? BobF>