As per title, I'm in need if some help deciding on an appropriate treatment for my daughters beloved "Nassa". He's about a year and a half old and around 6", 55g tank way over filtered with a corner mattenfilter setup, only tankmate is 4" albino bristle nose, 0 ammo 0 nitrite and less than 20 nitrate, temp 76-78f. The issue: he's just not been himself for a while, although still eating robustly. Right flank is slightly larger than left side, barely noticeable. He looses and gains color rapidly throughout the day. The main worry is a black splotch on right side that appeared over night two weeksago and he's been rubbing on the sandsubstrate here and there. After a waterchange(20-30%) the spot will nearlydisappear for a few hours, water changesare once per week usually but morefrequent lately. He seems to swim normally but has been sitting on the bottom in acorner occasionally but perks up aroundfeeding time. Been feeding peas for acouple days, effect has been minor. Normal food is hikari cichlid gold and hikari sinkingwafers, earth worms or frozen foodsoccasionally. Sorry for wall of text and repost(put it in wrong section), any help would be greatly appreciated.
