I had over 30 freshly hatched larvae in one container, then to make it easier to feed (brine shrimp) and clean, I separated them into two tubs, then as they grew, some faster than others I moved the larger ones into another tub, and so on. I am at 6 tubs at the moment, and I have a spare 6 tubs, which whilst feeding, I half fill them with clean water, then it is easier to transfer the babies over after they have finished eating and pooing. I have a bit of frogbit (plant off ebay) in each tub, and dont have a filter as the plant helps as does the doing the water change twice daily (only because they are fed twice a day.