I posted on the newbe forum for advice because my fish are dying at a rapid rate. The most visible sign/symptom is that their tails have rotted away. I have now lost nearly all the guppies at an alarming rate.I did a nitrite test that was clear. On the aquarium shops advice I have started a course of MELAFIX but the symptoms/circumstances described for Chilodonelle cyprini in Andrew post are almost identical. Should I continue with the MELAFIX. Please can you advise me??