I just did another test. Same results. I'm using the API Master kit, and I just got it about a month ago. I have stopped petting him because it could remove slime coat I guess. I thought it was just odd behavior too but he's been doing it for months and sometimes as I said my clown knife does it as well. Could it possibly be an external/internal parasite thats only on the bottom of the tank? I only think this because the fish that hang out in the middle to top water column never do anything like they do.