Enough to get a little run off, I wouldn't water again after that until you can feel the weights gone from the bag, thats one problem with the big containers with little plants but it will do fine. I think the moisture deep in the bag could cause the roots system to go down there searching and in the long run you could have a stronger root system? Will be interesting to see how it all plays out. How many day so o by before you water again?question, the plants are in 5 gl bags, i believe ... how much water should i give per watering/feeding per bag??