I recently got two leopard corys and then today, more or less on impulse, I added a schwartz cory and a panda cory to the tank. The leopard corys and the schwartz cory seem to be getting on fine but the panda cory seems to be a little lost. He'll swim with the others for a bit and then go off and sit by himself. Is he not bonding because he's a different species? If so, does that mean I need more panda corys for him to be happy? (would mean I would have to get a bigger tank and cycle it, which would be an enormous hassle not to mention cost)