I think it's a good question and it will be interesting to see what range of answers you get. I always have two containers going at a time, and rotate them between days. You want the BBS to be as newly hatched as possible, so you're getting as much of their yoke sack as you can. That's where the food value is. So keeping them more than a day starts to lose value. I have about 3 qts water in my homemade containers (inverted gallon jugs with the bottom cut out) and use at at most 1 tsp a day, usually end up throwing some out. You don't want extra sitting around in the tank for long fouling the water.