A couple weeks ago I had to treat my tank for Ich because my clown loach was covered with it. I used malachite green at half-strength for two 3-day treatments with a day off in-between and a partial water change. Everything seemed to clear up in the tank and none of the fish appeared to be stressed.

Yesterday morning when the clown loach came out of his house, I noticed a dime-sized bleached-out spot on his right side. He doesn't appear to be in distress or anything. And it doesn't look like the Ich did. I have no idea what caused it.

Any ideas?