Marine Velvet, I can't believe its happening to me.

[Aquattro]

Originally Posted by MarkoD

I understand it's not a cure. But would the benefits of decreasing the chances of an outbreak outweigh the killing of some microscopic foods?

From what I observed with MV, no, it wouldn't help. The outbreak has already happened, so adding anything at this point isn't going to prevent an outbreak. If it's MV, the only viable option to save fish is to catch them, put them in a treatment tank and treat aggressively for the pathogen. Or let it run it's course and see what's left on the other side. However, fish can build an immunity to MV, so while you may feel some fish are safe at the end, adding a new fish could set it all off again, with the old but infected immune fish infecting a healthy new fish.