Corys And Formalin/malachite Green

[blinky000]

I'm starting to lose the battle with costia in my community tank. I've done two rounds of methylene blue to no avail and my betta in particular is really starting to look pretty miserable. I have some FMG have I've been researching if it'll be ok with all the inhabitants at a half dose. So far it sounds like a good option but I'm struggling to find anything definitive when it comes to treating corys and otos. I've read through a few old posts on here and it seems to have worked fine for them, but I've also read that it can be quite toxic to cats. What kind of dose would you recommend for them?

 

[KISSfn]

Good read here.

http/www.skepticalaquarist.com/ichthyophthirius

 

[snazy]

Costia doesn't survive high temperatures. Try increasing the temp to 30 degrees maybe. Not that corys and otos will like it but they should survive it temporarily considering the life cycle of costia decreases with higher temp and it shouldn't survive over 30 degrees.
And also find the root cause as in order for costia to overtake the fish's immune system there must have been some type of stress present in the tank.