rubbing

Four years of happy fish keeping and the mysterious flashing that came and went a couple of years ago is back. Its driving my fish and me crazy.   No other symptoms on the fish, no white spots, no visible parasites, no stringy poo, no heavy breathing, no loss of appetite, no hiding, no fin...

My panda molly rubbed itself against a rock earlier, immediately after another yellow molly did the same, just a quick swift rub kind of like how a cat rubs his mouth up against things.. Upon research this can be a symptom of ich.. I'm not sure this is the problem as it doesn't happen often, I...