Hi, I have a sterbai cory which I believe has a minor case of septicaemia. It is at the base of the table and it looks like a pail red line. I have some furan 2 and would normally just give the tank a dose but I have about 30 2 week old cory fry. Will they survive the treatment? I have never used furan 2 before and am wondering if I need to turn my filter off while dosing. Can I leave it on? Thank you!