Is this aiptasia ?

[phossart]

 

[Reefer_Marc]

Not an expert, but it doesnt look like aiptasia to me. Maybe hydroids?

 

[MossyFroggyLove]

If i am not mistaken, that is a young hidroid. I have seen those in my tank before. They look like little jellyfish before settling down and transforming into a hidroid. But, i cant confirm.

 

[EnterName]

Medusa state of a hydroid. If your tank is relatively young they are very common and will most likely disappear over time.

There are some "horror stories" about hydroids but most young tanks have them for some time until they simply disappear.

You might also notice white thin tentacles attached to the rocks soon. These can irritate corals, but in a few months they are gone.