you can go with 2 or 3 gallon buckets. BUt you will have to keep a close eye on it, because your pH could blow up really fast since their isnt too much water to balance everything out. The grow sight is probably in our house so you have the conveinience to checking up on it whenever you want. Plus if you only have 4 feet to grow with the smaller buckets would be perfect to control the heighth.