Are these flatworms?

[Joe Rice]

Thousands of these suddenly appeared in my frag tank after I did a deep cleaning and moved a couple of corals in from my display tank. They're between 1mm and 3mm in length.

I've never seen them before in either tank and it's been many months since I've added anything to either tank so I'm a bit mystified where they came from.

 

[vetteguy53081]

Yes

Siphon out as many as yyou can. Are there a few or many?

 

[Joe Rice]

Yes

Siphon out as many as yyou can. Are there a few or many?

Several thousand, I'd say.