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FAQs about Marine Protozoans

Related Articles: Marine Protozoans, Marine Microbes, Marine Virology, Marine Mycology, Marine Bacteria, Phytoplanktonic Marine Algae, Invertebrates, Marine Plankton, Taxonomy & Biological Classification

Related FAQs: Marine Microbes, Marine Virus, Marine Bacteria, Marine Funguses, Marine Plankton, Phytoplankton, Live Rock,

Snails?     8/23/17
<Howsit Ryan?>
My local aquarium shop suggested that I submit a question about some critters in my tank. The attached images show these "sand-sized" organisms (about 1mm in diameter) blooming in my tank.
<Neato! These are Foraminiferans! Sign of a healthy system, lack of predators>
They have been there for months and seem benign, or maybe even helpful (eating algae?), though they do obstruct the view of the tank some. There are thousands of them in the sand bed, on the rocks, and on the glass.
They move very slowly...as indicated by some time-lapse video. The close-up photos were taken with a macro lens.
Can you provide any insight? Are they helpful? Harmful? Should I be concerned?
<No concern; are helpful... Enjoy them while you can, as changes in your system will result in their crashing population wise... other life becoming more dominant in time>
<Thank you for sharing. There's a bunch on the Net (even WWM) re: https://en.wikipedia.org/wiki/Foraminifera
Bob Fenner>

Re: Snails?     8/23/17
Excellent. Thanks for the info Bob!
<Welcome Ryan. BobF>

red macro algae? coral? sponge?     1/16/14
Hi Crew - first, thanks for an extremely useful website - whenever I have a question that I cannot find an answer to - your site is one of the few places that offers exactly the right answer.
I have 60gal reef tank that I have been VERY patient with.  I started it up 9 months ago and just bought my first corals last week.  This was in part as I was fighting a diatom bloom initially, then a seemingly endless Cyano problem until recently.  The major reason for the Cyano die off/control now, was switching from an algae scrubber to a properly rated skimmer, and using only foods with low P content.
 This has helped immensely and I got to the point of being comfortable putting corals in.  Coralline growth has become markedly more prolific since then too.
<Ah, good>
Now my question is this: while fighting the various plagues (including a 300+ Aiptasia outbreak - thank god for berghia nudis), I noticed a really pretty hitchhiker on some of my live rock.  So this started growing during a time when even though my kit readings were essentially non detect, but the presence of Cyano/green hair indicated that I had a surplus N or P issue.  At first I thought it was a type of coral, and then considered sponges - but then someone on a forum suggested that it is likely a red macro algae - rhodophyte of some form?
<This is my guess as well (or a Foramiferan)... I didn't see (under magnification of your photo) any pores/openings... that would be present in Corals, Poriferans>
 It is a soft tissue, plate-like structure that is now roughly the size of quarter (with about half a quarter "depth" to it). There is a second larger example growing at the back of my tank, out of reach of a decent photo - that specimen is roughly two inches wide, an inch high and an inch deep.
Any thoughts?  Is it more likely a red algae?  Finally - this is the important bit: is it good or bad?
<Much more good than bad... mostly as an indicator of healthy conditions here. Not toxic>
 Should I be considering removing it, or if my water chem. is truly coming around, should this guy just die off/starve anyway?  Any thoughts would be greatly appreciated.  It's really pretty and I'd prefer to keep it if it isn't doing any harm...
and image attached for good measure too.
<Cheers, Bob Fenner>

Re: red macro algae? coral? sponge?     1/16/14
Well that's good news then!  Thank you so much for the speedy and reassuring response - you guys are the best!
<Ah, welcome Mark. BobF>

Live rock growth      10/28/13
Hello crew!
<Hey Em>
A rock in my 90 gallon reef has recently sprouted a patch of red sticks with stiff white whiskers. They are quite beautiful and don't seem to be bothering the mushrooms they are growing in between. Can you help ID?
<Mmm, have seen this before... I believe this is a Foraminiferan... possibly Homotrema rubrum. Not harmful; au contraire; indicative of a healthy set of conditions here>
<Welcome. Bob Fenner> 


Need help with pick growth on rock:  Probable Foraminiferan – 3/10/12
<Hello Amanda, Lynn here today!>
I'm trying to figure out what could possibly be growing on one of my rocks.
<If it’s soft, it’s probably an alga of some sort.  If it’s hard/stony, then it’s more than likely a harmless, beneficial, and very pretty Foraminiferan in one of three genera: Homotrema, Miniacina, or Sporadotrema.  All are in the family: Homotrematidae and are found in tropical waters. They’re also similar in color, in that they typically range from shades of pink to reddish (sometimes a bit orange), can be branching, and seem to prefer more protected areas away from strong light. They feed by means of fine, hair-like structures extending from the tips that collect particulate matter from the water column. All in all, they make nice additions to a system.  For more information, please see the following links:
See FAQ:  “Unknown Pink Growth: Foraminiferan -- 3/2/10”:
Homotrema rubrum/rubra:
http://www.foraminifera.eu/single.php?no=1000968&aktion=sucheMiniacina:   http://www.biolib.cz/en/taxonimage/id4217/Sporadotrema
http://www.foraminifera.eu/single.php?no=1001903&aktion=suche >
<You’re very welcome!>
Amanda Moore
<Take care, Lynn Z>

ID this thing ... - 2/9/11
Hi Crew member,
Attached are several pics of something from my tank. The bright red ball appeared, stuck just under my RBTA.
Tank is a 72G Bowfront with a 30G sump/refugium, FL live rock, DSB - running for about 1.5 yrs. Known inhabitants are mostly common to the hobby - Scopas Tang, Niger Trigger, Blue Damsel, Blueheaded Wrasse, Engineer Goby, (2) Clowns, Coral Banded Shrimp, RBTA and a mix of Atlantic/Caribbean and Pacific corals including SPS, LPS and softies.
The brightly colored fuchsia ball is about the size of a pencil eraser, has a felt-like surface, sticks to the live rock, fish won't touch it, seems to have a soft "shell" that has split open. It doesn't appear to be porous
like a sponge ...but that was my first guess.
<Mine too.>
Any idea what the hell it could be?
<Are there any apparent openings (two, dissimilar in size) on the surface?
If so my guess would turn to a sea squirt/Ascidian... At this size this could be a Foraminiferan... http://wetwebmedia.com/marprotozfaqs.htm
Thanks for your thoughts.
<Do send along better resolved images if/when you can. Cheers, Bob Fenner

re: ID this thing ... - 2/9/11
Hi Bob,
Thx for the quick reply. And my eternal thx for access to your wealth of knowledge! My Scopas will forever be in your debt.
Those are the best images I could get - no macro lens and a bowfront tank (
the digital camera really struggles with angled shots and focus).
<Ah yes. Am familiar>
It does not appear to have any well formed openings. The surface is like dyed felt.
The casing-like structure could be a leathery shell or random growth on the surface that was broken when the ??? grew a bit.
I looked up FORAMS HOMOTREMATIDAE and it is a possibility. Perhaps in an early stage of growth - before branches form.
For now, it has drifted away to some dark recess of the tank.
<I'd leave it be; enjoy it!>

Help with ID of mystery coral 1/9/11
Greetings and Happy New Year Wet Web Crew!
<... groan... seven plus megs of pix... We ask folks to limit these to a few hundred Kbytes>
I am hoping you might be able to ID a mystery coral (I will admit to not being 100% sure about that, Heisenberg not withstanding) that's been a delightful "hitchhiker" on some live rock I purchased about three months ago. Unfortunately I do not know where the live rock originated before it found its way to my LFS.
There are a number of these creatures that can be found around the system, but all are in shadowed areas, primarily on the underside of rocks. They are perhaps 1/2 in length at this point - it's hard to tell with all of them because they seem to grow in crevices the depth of which is difficult to gauge.
The polyps/filaments are always extended. Day, night, doesn't matter.
They are hard/rough to the touch (early on I thought it might be a slime/red algae because there were no polyps visible. I was glad to be wrong there!
I have searched the site (which is excellent!) as well as combed through Borneman's book and have also tried a few Google searches but nothing seems to fit. I've read descriptions of both Tubastrea and Sponges that could fit, but have ruled out sponges primarily because when the rocks were moved they were out of the water for 10-15 minutes and growth continued. Tubastrea seems unlikely as I am not feeding these poor things specifically yet they appear to be thriving. We originally thought it might be Montipora but now that it's large enough and extending those long extensions, pretty sure that's not it either.
Please see the attached photos for details. Unfortunately it is nearly impossible to get a good photo of the skeleton as its polyps/extensions obscure them and, well, they're always out. From watching the growth they do appear to share a base and "branch" from there (there is another grouping in the photos to the top/right that appears to be doing this), but there are other growths like this that are singular (I believe you can also see some of them in the photos to the top and right of the larger grouping). Seriously, this stuff is all over. Only some of it, however, thrives - those groupings that are in the shadows.
Hoping someone has some idea what these are and if there's anything I should be doing differently or even if I should be very, very afraid of it. You never know...
Thanks very much in advance!
<Likely Ascidians... see very similar here:
Bob Fenner>

Re Hydroid? Cnidaria? Sponge? Our mystery guest is... 1/24/11
Greetings Wet Web Crew!
<Hello again Lori!>
I had written a couple of weeks ago but others have had issues with my e-mail and given I included several very large hi-res photos, well, never hurts to ask. Because I know you can't possibly be busy updating the site or answering other queries or doing other productive things (like jobs and stuff). :-)
<Oh yes>
In any case, I've continued researching while I waited and am now even more confused than ever. I've uploaded as hi-res a photo to Flickr as I can for your viewing pleasure:
Descriptions and other IDs on the site here seem to indicate it could be a Hydroid.
<Mmm, yes. I had replied to this query>
Or a Hydrozoan. Or perhaps a Sponge or maybe some strange communal relationship between one or more in some sort of twisted, undersea love triangle. Or maybe it's a coral of some sort? That'd be awesome but my day has been going such that I would not expect that to be the case. A photo in http://www.wetwebmedia.com/AscidIDF4.htm seems eerily similar, though the body of these and formations appear foliate and digitate in nature, though it's hard to tell whether the foliate forms are simply two or more fingers in a colony growing very closely together. Your answer to the query referenced in the FAQ above, by the way, pointed at Hydroid/Hydrozoans but after reading those FAQs this does not seem to be the case? Of course I'm not the expert, which is why I'm writing you.
<I do think what you have pictured is both Ascidian AND Hydroid... the "feathery bits">
The branches are firm. When they first appeared a few months ago I feared Cyano or slime algae, so I brushed at them and they did not give at all - they were actually fairly rough to the touch. So I continued watching. The rocks upon which they were growing were moved - and thus exposed to air - about a month ago to a 150g tank, which at first disabused me of the notion they were sponges but then again with the new arrangement these could be different growths.
The extensions appear quite rigid in the photo but close observations shows them to be more flexible, more like a polyp or tentacle than a rigid extension. There are many, many of these growths, but only ones growing downward in shadows on the underside of rocks or in crevices exhibit rapid growth and these extensions. Those in the photo have grown about 3/4" in the past month to extend out of the crevice they are in.
I'm running 1 14,000K HQI metal halide (150 watts) and 4 (39 watts) HO T5 actinics.
Any thoughts are greatly appreciated - they are interesting to see growing but if they're dangerous I'd rather remove them before they turn into a plague. I do have higher resolution photos but am reluctant to attach in case that's keeping my e-mail from being delivered. If you received my first e-mail but haven't had a chance yet to respond, my apologies. If you did respond and I didn't receive (which has also happened in the past month or so, or so I'm told) my apologies.
<See here: http://wetwebmedia.com/NonvertIDF56.htm
dated 1/9>
I'd buy you a beer to make up for it but I'm not traveling much these days. :-(
<If you're close by, I'll drive on over!>
Thanks for the great site and all the great information!
Lori MacVittie
<Welcome! Bob Fenner>
re: Hydroid? Cnidaria? Sponge? Our mystery guest is... 1/24/11

Ah, thank you very much for re-responding and my apologies about the size of the original photos. Will keep to minimum or use Flickr in the future.
<Ah, thank you>
Now I just need to figure out what happened to your response...hmmm...
<Yikes! Am not a high-tech kind of guy>
Many thanks!!
<As many welcomes. BobF>

Update: Is the mystery guest really Sporadotrema? Foram.! 2/6/11
Greetings (again)!
I have good news and an update/question regarding the "mystery guest".
The good news is I discovered you were caught in the big technology QT in the sky. My SPAM filtering service has been updated and unlike my system your e-mail will go straight to the DT.
<Ah, good>
You (well, perhaps not "you" per se but BobF unless this is BobF and then "you" really does mean "you") had suggested my mystery guest was both Ascidian and hydroid. I was reading about pods (because I found tons of them in both my systems - wheeeee!) and followed a link that led me here and there and then to this image: http://www.nevillecoleman.com.au/gallery/image-listing.aspx?ImgGroupId=7839
<Mmm, could be!>
That certainly appears to be the same critter as in my photo. A Foraminiferan identified by the image as "Sporadotrema meserfericum".
I'm fairly certain of the id based on the photo match - even the test appears the same as described, especially as occasionally I can see particulates caught in it that eventually disappear. I did a search on WMM and did not find any further information on Sporadotrema but did find more on Homotrema rubrum. Interestingly the photo around which the discussion of Homotrema is based (here: http://www.wetwebmedia.com/lridfaq7.htm) looks a lot more like the one in the aforementioned link/image that describes it as Sporadotrema.
Now I've been trying to read about forams (which is fascinating and has led to the ID of some of the other growth forms in my system which appear to be Homotrema rubrum) but I'm not finding much about Sporadotrema except in lengthy very scientific journals that are more confusing than anything else. For the most part I gather these are (a) not dangerous, (b) not toxic, and (c) require very little attention on my part. Do you concur with this conclusion? Is there something else of which I should be aware?
<I do concur w/ these statements. Not harmful esp.>
If I'm reading things correctly they're both Foraminiferans so it shouldn't really matter but now I'm curious (and a little excited to perhaps have found an answer to the question "what are those 'bearded things' growing in the system??").
<I do (still) think these are another organism. Do you have access to a dissection 'scope?>
Thanks in advance (for wading through this message and for all the great information you provide!)
<Do please read here: http://wetwebmedia.com/marprotozfaqs.htm
Lynn's ID et al. re Forams. BobF>

Sea Grape 4/17/10
Hi Bob, Lynn,
I wonder if you know what this object is. A friend found several of them on a beach in Florida. As you can see, they're about the size of a penny. They are grainy like rough paper, slightly glossy, and with a hole at one end.
They look a bit like the cells of burrowing wasps to me, but I don't think that's the case of they were found on a beach. Any ideas?
Cheers, Neale
<Mmm, my best guess w/ these pix, descriptions is that these are Foraminiferan skeletons. Lynn? BobF>
Re: Sea Grape 4/17/10
Thank you Bob. I'd considered that idea too, e.g., Gromia spp., but thought these specimens were perhaps rather too large for inshore Forams.
Cheers, Neale
<Might/could have been transported from deeper water... air filled w/ decomposition of other life that had come to reside w/in. BobF>

Sea Grape, Lynn's go 4/17/2010
<Hi Bob, Neale>
I wonder if you know what this object is. A friend found several of them on a beach in Florida. As you can see, they're about the size of a penny. They are grainy like rough paper, slightly glossy, and with a hole at one end. They look a bit like the cells of burrowing wasps to me, but I don't think that's the case of they were found on a beach. Any ideas?
<The first thing it reminded me of was a praying mantis egg case: http://2.bp.blogspot.com/_lDfVXMCBuu0/STthPwvtTkI/AAAAAAAACBA/NPcU2zgD-fg/s1600-h/praying+mantis+egg+sacs.jpg
or a wasp gall, but it could be something like a bleached Prickly Palm nut (Acrocomia spp.). They vary in size, can range in color from black to bleached white and have a rough texture (before polishing). There's a whole group of people that collect all sorts of "sea beans" on beaches. I have a few myself, but have never seen anything like this. Here are a few examples (some have been polished):
Prickly Palm nuts spread across upper left area (note the white one):
Here's a before/after (polishing) of a Prickly Palm nut: http://1.bp.blogspot.com/_uuHPvedMUw4/SRdJ9iTRl9I/AAAAAAAA
If I had to guess, I'd say it's a Prickly Palm nut. If not, my next guess would be some sort of deserted, combination mucus/sand burrow, or subsurface egg chamber made by what I don't know, that was exposed at some point. I don't remember the sand in Florida being that white but it's been a while since I was there. Hope that helps! Take care, Lynn>
Cheers, Neale
Hello Lynn,
The sea grape doesn't have the three-fold radial symmetry of the palm nut, and is far too thin and light anyway, so I don't think that's right. But your idea of some sort of hardened burrow makes sense. Dried mucous would give the glossiness I'm seeing, and it could easily be stuck together from sand. What sorts of animals lay eggs in subsurface burrows?
Cheers, Neale

Unknown Pink Growth: Foraminiferan -- 3/2/10
Hi all!
<Hey Debbie, Lynn here today!>
When I designed my acrylic 35 gallon SPS tank, I had a 10 gallon refugium set up to be next to it as a display refugium. I used pond foam to create a sort of dark cave for the Rusty goby and peppermint shrimp that I put in there along with some rubble, hitchhiker bivalves, sponges and the like. This section gets no light except for ambient room light and you still need a flashlight to see in it. I had sun corals in there, also, but moved them, as you can see there's a baby that got left behind.
<Yep, I see it.>
Several months ago I noticed this pink growth around one of the bivalves. It was so small I couldn't get a good picture to send in for identification. About two weeks ago all the tips were covered in a white spongy material and I thought some sponge had managed to start growing on it. However, after a few days the "white stuff" seemed to just disintegrate and the coral appeared just fine. But now I've started noticing these pink/red spots like the one under the word "New" that are starting to grow. I've counted about 40 that I can see. A couple are by the front and they have the same type of tentacles as the main colony. They're about the size of a pinhead. The main colony in the picture is only about 3/4 of an inch wide so it's quite small.
<Looks like you've got a nice little Foraminiferan colony! Forams are harmless, filter-feeding Protozoans that come in all shapes and sizes. From the looks of things, you have a common, stationary, branching variety called Homotrema rubrum. The pink coloration and presence of fine filaments (aka rhizopodia -- used for feeding) extending from the tips are distinctive.>
The tips have thin strand-like tentacles and I attached a close-up picture of those as well.
<Nice photo showing the rhizopodia! One thing I see that may not be a Foram is the small, darker object between the two light pink Foram tips. The fact that it appears so shiny and smooth makes me think it's an Ascidian/Tunicate, but it could just be a smaller Foram. Color can vary with these. If you get a close look at it and see rhizopodia, then it's definitely a Foram. Tunicates don't have those.>
I'm unable to reach it, so I can't tell if it's spongy or hard, although the tubes appear to be hard just by looking at them.
<Yep, they're hard/stony-feeling.>
I'm hoping that by chance somebody may have come across something like this and knows what this is.
<Oh yes indeed. I've had these in my tanks for years and love 'em!>
I'm stoked that it spawned in my tank so I'll be documenting their growth. Any information or insight would be great.
<This link should be helpful: http://reefkeeping.com/issues/2003-07/rs/index.php
Be sure to Google WWM also, as there have been several references to these over the years: http://www.wetwebmedia.com/Googlesearch.htm >
<You're welcome!>
<Take care, LynnZ>
Is this Velvet or Crypt, and what are these white things 1/4/08 Hello. <Greetings Joe> Thanks for all the helpful information that you provide. I have spent dozens of hours reading on your site, and yet I know that I have so much left to discover and learn. <As do we all> I have a 120 G saltwater Fish only tank in which there was a massive die off all within a week period from first signs (cloudy eyes, breathing difficulty, death). I attributed the deaths to /Amyloodinium ocellatum / due to the rapid onset and a few white "dots" that appeared on the fish/. / The first picture (100 X Mag) is from gill scrapes taken and are representative of what was found. Can you confirm these as either /Cryptocaryon irritans or //Amyloodinium ocellatum? <They do very much look like trophonts of Amyloodinium... do you have Iodine that you might test them for staining?> /All but the initial fish that helped cycle the tank were aggressively quarantined with Chloroquine and rotated with QT tank change every 3 days for four changes, but as I have sadly learned, any fish can introduce disease into the tank. <Yes, actually, anything wet>
Amyloodinium trophonts
The Main tank was left without fish for 11 weeks. 4 weeks into the fallow period, I began seeing small white dots, about 1/10 mm in size forming on the green algae on the glass, and where they would appear, the algae would disappear in an expanding circle of small white dots. <Yes... I see... what appear to be a small snail, but could be a Foraminiferan... or...> The second picture is an microscopic picture of one of these. These are not moving on the glass, and much smaller than copepods which are moving on the glass.
Foram most likely
In the midst of the smaller dots, there are also larger, about 1 mm in size cream/white/tan colored dots that as can be seen in the final picture taken of the glass sides of the tank. These are slowly moving on the glass and removing/eating the algae as they pass as demonstrated on the picture. Under the microscope, the larger dots appear to be larger versions of the smaller ones, too dense and dark to photograph well. Is there any chance that these are the developing tomonts of /Cryptocaryon irritans or //Amyloodinium ocellatum/ left from when the outbreak occurred? <Mmm, not on the glass, moving, no... Is some other form of life.> Are these something I need to be concerned about? <Not the stuff other than the Amyloodinium, no> Thank you for your help as I work thought the process of getting my tank healthy again. Joe
<Nice pix Joe. Thank you for sharing. Bob Fenner>
Got me...

Foraminiferans Irritating Corals? 11/21/2008 Hello to whomever is answering emails today :D <Hi Miguel, Mich here.> I've been having an issue with what I think are Marginopora vertebralis, which I just Id'd thanks to the handy search function on your site. <Looks to be so.> For a back story, I've had issues in the last few months with LPS peeling slowly, and every time on the peeling flesh I find these Foraminiferans. It seems like they're slowly irritating the corals to death as they feed on whatever it is that they're feeding on the live rock. <Mmm, does not necessarily make it causational.> I've included a picture of what I think is them irritating a coral. <In researching I have not found information to support this, but that does not mean it is not possible.> This is how all of the peeling LPS tissue in my tank looks like, you can see that at 12 and 6 o'clock they are digging into the flesh of the coral, and especially at 5 o'clock you can see a smaller one digging into the coral with a distinct peeling flesh next to it. <This is unusual.> At the very bottom right of the image you can see them working into the flesh as well, and in the top left there is a white spot on the coral that's actually another one that has just attached. <I see.> I'm not sure if these are the cause of the problem or just bystanders in another tank issue that may be going on, but it's a bit coincidental that they're always right at the edges of the peeling sides of the corals. <Some types of Foraminiferans feed on bacteria, perhaps the Foraminiferans are feeding on areas of decay.> One of my friends had a microscope, so I'm attaching several highly magnified images in order of magnification. <Cool!> They average about 1mm across, and in picture 4 there is a blob of green. <I see.> I'm not sure what that is but it's the only block in the Foraminiferan that had one in there, possibly it's feeding on it? <Is a possibility.> Thanks very much for your time, and I hope things are well! <Thank you Miguel.> Miguel <Cheers, Mich>

Nice pix! RMF

Looks like a UFO, but it's a Foraminiferan! - 1/23/08 Hi Guys! <Hi there, Terje!> Can you help me identify this brown thing? The picture should be approximately 1:1 (on a 15-19" monitor :) ) = 3mm. <<ufo.jpg>> <Wow! Looks like a very pretty little Foraminiferan test. Forams are harmless, single celled organisms ("Protists") that are shelled and supposedly feed on bacteria and organic matter. Please see these links for photos and more information re: http://home2.pacific.net.ph/~sweetyummy42/hitchodds.html http://www.reefkeeping.com/issues/2003-07/rs/index.php > Regards
Terje Midtb?
<Take care -Lynn>

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