jellyfish (hydroid?) in my refugium?

I have a refugium chamber in my sump that is not really "in use" because of a leaking baffle (bad design on my part). Anyway, I turned on the light to check on it this morning and noticed a bunch of little jellyfish looking things swimming up to the surface and then floating back down. Are these hydroid jellyfish?

Jellyfish in refugium? - YouTube

 

Very cool. I don't think that jellyfish would attach to the glass like that though. I could be wrong though, and if I am would you want to sell some

 

Yes, those are the hydroid kind. I saw them early on in my tanks life, but haven't seen any since. And looking at the video, I'm guessing your tank is new too

I don't think they are a problem, unless you are trying to raise baby fish or other tiny things.

Rick

 

So cool;D

 

Droids will indeed wax and wane with your pod population or in the presence of lots of small live food (such as BBS). As mentioned, they aren't an issue for larger fish, but will kill fry and small specimens (such as some of the smaller gobies).