Ghosts in my refugium 1/8" long??

[mweber]

about 2 weeks ago I noticed a few odd creatures crawling on the walls of my 20 gal refugium. They look somewhat like a jellyfish. They appear to be a light white, semitransparent bag of water about the size of a BB. At one end they seem to have 2 limbs or tails enclosed in a small pair of pants. They seem to be eating algae and seem to move by filling and exhaling as they grab the surface with the ball area. They are not round but rather flat looking at them from the top of the tank.
I now have 100 or so of them. All other life in refugium seems normal, pods, shrimp, and worms, excep that my caulerpa seems to be hurting (see other post for that unless you think it is related)

My question. What are they? Good? Bad? Natural? Supernatural?

 

[BReefCase]

I have these all over the place. Since they seem to be especially thick on the glass near the "pod piles" I build in my tanks, I think of them as 'pod relatives of some sort. Beyond that I have no clue as to what they are, specifically.

I have them both milk-white and glass-clear except for a little bag of guts in the middle.

I've had them forever, so they don't seem to do any harm, at least not to anything in my tanks that I have ever noticed.

They can get quite large -- almost 1/2 inch or so, at times, but the really big ones are rare and that's the biggest I've ever seen them get. Populations seem to grow and shrink, in no particular cycle, for reasons that are not clear to me, although both DT's and the much-maligned Kent's phyto seem to make their populations boom.

I wouldn't worry about them. Just more life diversity and the sign of a healthy tank.

By the way -- is your Caulerpa "going sexual?" It does that as part of its repro cycle after a period of growth, and then totally collapses, which will really test your protein skimmer.

 

[RyanH]

I have these same guys. They seem to be more active at night too. Are they some type of a planaria or flat worm?

 

[esmithiii]

Can you post a pic?

E

 

[mweber]

Thanks on the ghosts. I'll answer the caulerpa question on that separate post

 

[kbauer]

I have the same little gremlins in my refugium and I was hoping someone could identify them. I don't think they're in the worm family or nematodes and I don't know where else to search. In fact I was delighted to see your post because I hadn't seen another reference to them, but since I'm new to the hobby I thought maybe they were fairly common and I was the only one who didn't know what they were! They are pretty interesting little creatures to watch. They are not in my display tank either.

 

[Rays]

RyanH,
Yes, more than likely. They multiply like rabbits, they aren't harmful, just a nuisance. I used to get a flashlight at night and suck out the ones I could get with a turkey baster. That was about three years ago. And, I haven't added any new LR since.
Ray

 

[tomocean]

I believe what you are talking about is a type of flatworm. They are harmless and I've heard them referred to as "caped crusaders".