What is this? Some sort of jelly fish?

[vetteguy53081]

Hydroids are related to jellies and part of their lifecycle they look very much like them and travel around like jellies. Hydroids come in many shapes and sizes as do their medusa stage of their lifecycle.

which is what I thought they were. Multiple stages

 

[Cristy17]

They can be, but easy to deal with. It's very common for them to show up then subside in newer tanks though.

Ok thanks. That makes me feel better. This tank has been running 11 months or so and this is the first time I have noticed these. Thanks for your input.