What the heck?!?

[Wolf89]

What the heck are these? Discovered in 10 gallon copepod breeding tank, nothing added in over two months, nothing but copepods and a piece of live rock. They move like jellyfish, but way faster. They also have a light sensitivity, ie when I use flash, the start jumping around. Are these guys bad or good? They look like seeds of flowers or something

 

[SomethingfishyPKNY]

What the heck are these? Discovered in 10 gallon copepod breeding tank, nothing added in over two months, nothing but copepods and a piece of live rock. They move like jellyfish, but way faster. They also have a light sensitivity, ie when I use flash, the start jumping around. Are these guys bad or good? They look like seeds of flowers or something

Maybe hydroids

 

[saltyfilmfolks]

The Medusa stage of hydroids or jellyfish.
Same basic thing.

 

[Big G]

Hydroids - Medusae they feed on plankton and other small particulates.

 

[Wolf89]

So they are good?

 

[saltyfilmfolks]

I wouldn’t add them to a tank , no.

 

[SomethingfishyPKNY]

They can sting. Especially tank mates like pipefish or ponies

 

[SomethingfishyPKNY]

They get in the tank via ocean water, live rock and live ocean sand. Can only avoid by using non live/ dead or cured products. Pretty much unavoidable otherwise.