I would think that having a larger group of mixed corys would keep them more comfortable than an undersized group. I've never tried it though.. I currently have 7 panda corys in one of my tanks and 6 juili in another. I've had them about 2yrs. Cute and active little things. They've all stayed small. I feed them sinking shrimp pellets after dark to minimize the other fish getting the pellets first.