either ick or velvet. if you're a local just put a medication called 'nika' general aid into the tank. and it'll be fine. increase the temp to around 28-29 for 2 days and make sure dont turn on the lights.. or you'll get a devastated tank like mine last time. well some of the upside down catfishes din survive as they are scales fishes. the others were ok.. might save u some casualties.