I have seven discus in a 75-galloon tank. They were all introduced at the same time about 3 months ago. Six of the seven are doing great. About two weeks ago the seventh turned black started hiding
and stopped eating. It looks like it is about on its last leg. I have a couple of questions though.
1. Should I quarantine it?
2. What should I treat it for?
3. Should I treat the other six even though they appear to be very healthy right now?
1. Yes. You should quarantine it in the hospital tank.
Treat her with Acriflavine solution plus salt.
2. The other six you can treat them with Formalin.
Dosage: 100 liters of tank water / 2 to 3 ml. of Formalin.