I've just had a massive fish die-off in my 72gal freshwater tank. It was the most precipitous die-off I have ever experienced. Water quality tested fine across the board (74deg, ph 6.7, NH3 0, nitrates/nitrites 0, ORP ~400). The first morning I lost 2 large angel fish, a paradise fish, a belonglanis, 2 clown loaches (that were over 8yrs old). Over the next 48hrs I lost a younger clown loach, a lge Australian rainbow, black khuli loach, lge algae eater (>6yrs old), red tail shark, synodontis and I decided to euthanize an 8yo, 12in pleco.
On the morning of the initial die-off I immediately began treatment with LifeGuard.
None of the fish had any outward signs of disease. Those that we saw die (that didn't die overnight) went from lethargy to death in a matter of an hour or so.
The only fish with any outward signs was the large pleco. We noticed this morning that he had clear pustules measuring between .125 and .25in on both lower edges of his tail fin, in areas of his pectoral fins and some on the base of his dorsal fin. We hadn't noticed this prior to this morning (although he was hard to observe since he liked to hide behind a stone wall in the tank). A small number of these pustules had blood and there was some blood streaking in fins. The pustules were thin-walled and undulated in the water.
We took some pictures (not fabulous quality unfortunately) of the pleco that I'm posting. Obviously I need to determine what the underlying casue of this plague is and am hoping you folks can help me so I can save the remainder of the community.
Thanks and Happy New Year.