What I found on some irritated zoas

[Triggreef]

Saw a couple that looked mad so I got out the macro camera. Could just barely see a white thing on one of them with my eyes only but the macro gives a better view.

Hydroid? @Lionfish Lair

 

[saltyfilmfolks]

it appears so yes. but not the typical colonial ones. they usually burrow in rock.
tooth brush time.

 

[cloak]

Hydroids?

 

[A. grandis]

Hydroids.
Siphon them up while you scrape them off with a pair of fine tweezers.
If you use a tooth brush you'll take the risk of braking them in pieces and loosing around the polyps.
Easy to find them. Just look for the irritated polyps.
If there is one there is more!!!

Grandis.