ok i got a large one and he has been great. i put an air stone in the tank because i have been having trouble keeping the no3 down in the tank. the bubble wall is next to the edge of the tank and my larger of the two will swim into the bobbles and into the wall and trys to swim through the wall it is kinda strange. he has never done this before is there something with the bobbles that is confusing him if i move it to the middle of the tank will it upset my catfish? has anyone had this happen before please give me some advice on what might be going on thanks i just dont want him to get hurt from rubbing his nose