PLEASE HELP!

[mikaylab3]

I have had my seahorses for about a month now, they have settled nicely and seem to be enjoying their enclosure!
today I purchased a new seahorse and a starfish, they have been acclimated and seem to have settled nicely!
After a few hours I have noticed that tiny white spots in my tank!!!
have I potentially introduced a pest or parasite into my tank?!

 

[lucyretz]

im not well versed with sea horses so im not comfortable giving advice, but the ID is hydroids.