Clear organisms floating

[Craig2051]

I just recently noticed that there are very small clear organisms floating in my reef tank. I'm not sure if they are alive but they noticeably seem to have legs. They just move with the current in the tank. Currently I only have 4 hermit crabs, 4 snails and 2 clownfish in the tank. Has anyone seen anything like what I am describing in their own tanks and have an idea what it could be?

 

[Craig2051]

I also have one small colony of zoanthids! Sorry forgot to add that!

 

[Lee]

Do you have any pictures? They could be Hydroids.