Hydras? Hydroids??

[JerryJ]

In the FOWLR tank I'm starting up (my first) I have one rock with about 12 things on it that look like the freshwater hydras everyone studies in high school biology class. They're about 1/8 inch in size, with a central stalk and exactly eight arms that stick out sideways. They're white, although on the bigger ones the arms look a bit greenish. I assume these are some sort of "hydroid"?? They don't look like aiptasia anemones to me, but as already noted I'm new to this! Do you think they will proliferate in the tank, and can they hurt other organisms? I want to get some cleaner shrimp, gobies, cardinal fish, etc. The "hydroids" are obviously too small to eat even a small fish, but can they sting them? Will peppermint shrimp or other scavengers eat these hydra things?

 

 

[DaveS]

Look up mojano and see if that looks like you bigger ones.

[Coral Hind]

Can you post up some pictures?

 

Hydroids can spread fast in a tank if there is a good food supply. I don't remember anything ever eating them but maybe someone else does. I would just remove them now so you don't have to worry about them.

 

 

 

[zygote2k]

I'd let them live and see what kind of cycle they have. You might learn more about them that way and actually figure out what will eat them.

[JerryJ]

Okay...I'm attempting to attach a picture of my hydroid thingies. Hope this works.

[Coral Hind]

Those are green star polyps. So much for your FOWLR, you might as well go "reef" now.

[JerryJ]

Ohhhh...so the purple stuff they're attached to is part of the organism, right? I was thinking it was coralline algae (hey, I'm a newbie, purple is purple to me). So apparently this is a photosynthetic coral (hence the green tinge?) that is fairly hardy and may survive in my tank? I don't have reef-type lighting, but the patch of star polyps is in fairly shallow water under the lights, so maybe it will be satisfied with my FOWLR environment. I assume if the coral does well, I'll get a lot more of these polyps sprouting out, right? Will the polyps develop more intense green coloration eventually?

[Coral Hind]

Yes, the purple stuff if the mat or base to the coral. GSP is very hardy and it does not require a lot of light. It will develop more polyps and the green will get darker if it gets enough light. Google image search "green star polyps" to see what it will look like.