jlemoine2

I'm guessing it looks like a spaghetti worm, a harmless detritavore.

It doesn't look like a tube worm or spaghetti worm. It's not completely clear from the photo but it appears to be lacking any kind of segmentation in its body, which excludes it from all segmented worms (bristle worms, tube worms, spaghetti worms, etc). Plus, the oral tentacles look far too thick and I've never seen them branched like that on a spaghetti worm.

Judging by the fleshy-looking branch oral tentacles and the knobby body texture, it looks like a tiny sea cucumber, but I am not completely sure. If they are sea cucumbers you may want to get rid of them 'cause they can be difficult to keep alive, and they release very powerful holotoxins if they are heavily stressed or dying. Like I said, I'm not certain about the identification. It may be difficult but can you get a better photo, especially one of the largest ones? Do they have any tiny "tubes" along the length of their body that they're using to grab onto the glass and move around? In what way do you mean they walk like a starfish? (Starfish and sea cucumbers are relatives). Do they stick their tentacles into their mouths one at a time? You could gentle move one into a low-flow area to get a better idea of how they actually move.

Thanks for the replies. I said "walk like a starfish" because the oral tentacles movement when "walking" around reminded me of a serpent starfish. The tentacles would reach and pull the rest along. Sometimes the tentacles also overlap each other while "walking". I have not observed them sticking tentacles into their mouth. They only climb the glass in low flow areas, which is mostly everywhere in the refugium. They seem to like it by the surface of the water. Most of the time, I can only see the long bodies, as the tentacle portion is hidden by the frame of the tank. The only one I've seen in the display was crawling along the sandbed close to rocks, there is too much flow for it to get to the glass.

The picture above was the biggest one available at the time, and it was difficult getting a macro picture with the stong light behind it. Since they are fairly active, even in the light, I'll try and get a better closeup of the body to see if we can see any of those tiny tubes along the body. The body for the most part seems to just dangle free. Looking at the picture above, the body clearly has nodules, and close to the outside arch on the upper portion, one of those nodules seems to be a little longer, perhaps it is one of those tiny tubes.

Thanks!

-James

Do you know how to use exposure compensation on your camera? It'll either be a button with the +/- symbol, or somewhere in the menu, set it to something negative like -1 or more, and it'll underexpose and get more detail out of this critter under the strong light.

I see what looks like a tube near the head. How many of the oral tentacles do they have? I can count 8 in the photo but I'm not sure if there are more that is out of view. If it's a multiple of 5, it's another sign that it's a sea cucumber since starfish and their relatives usually are built with multiples of five.

Good tip gerbilbox. Well, I have been unable to get any better pictures, none are on the glass on the front pane today... my refuge is only viewable from the front.

However, I have made some more observations. They do move tentacles to their mouths in a seemingly rythmic pattern. While on the glass, they originally appeared to crawl around by those tentacles, but after watching a bit longer they are stuck to the glass with at least a portion of the front end of the body... the tentacles do seem to help with movement. While on the rocks, I saw one that had itself errected up into the water column, looking a bit like a tiny feather duster... so it's lower portion of the body must be grippy as well.

I have at least 20 of these, my chaeto is crammed with them... .which is probably the source. I receievd it from reefcleaners.org.

I think these are sea cucubmers, particularly the variety known as "medusa worms". Searching for that in Google yields a number of photos and articles with critters that look like this.

I'm not sure I can remove them all, and they seem to be multiplying. Most of the articles I read indicated that they are toxic if they die... usually from starvation in reef tanks. Hopefully, they'll start kicking off while they are small, so impact on my tanks are minimal.

Thanks for the ID!

You can probably ask ReefCleaners if they've seen them before and provide some insight. It looks all but certain to be a sea cucumber to me, but IDing by photo is not that reliable. I usually see sea cucumbers slowly move one tentacle into their mouth, take it out, and do the exact same thing with the adjacent one. Never heard of them walking on their oral tentacles, but I am not a sea cucumber expert.

I've never heard of medusa worms refer to any kind of sea cucumber, but then again common names are not very reliable either. I've only heard of medusa worms refer to segmented worms from the Family Cirratulidae (relatives of the bristle, featherduster and tube worms) :P

They're really fascinating and there are some really beautiful sea cucumbers, but I've read that they're generally not aquarium friendly animals so be careful.