I actually use 3ea 2 gallon buckets, I don't raise many fish and by keeping three I can manage crashes easier. However I've not had a crash in a long time, I change their water out once every 10 days or so, feed lightly and have not had a shortage since I started this system.
I'm moving all this out to my shop in a special work area, and will then move to two 5 gallon containers to save space (they are tall ones).
-Paul-