recently I have been trying to raise a bullhead. Got him out of my bait bucket on Thursday. He is in a 5 gallon bucket that has rocks, sand, sticks and a cave. I have an aquarium air rator in the bucket also. Water temp is around 50 degrees. When i checked it out today the bullhead was on the top of the water ( not normal at all) and was swimming very erratically. He has a big grey spot on his gills extending downtime body a bit. Also put a minnow in as a tank mate. Minnow is fine. I have only feed them once on Tuesday with fish flakes and I didnt give them very many, maybe 2 or 3 that i had crushed up. Anyone have any idea what happened and how I can fix it?