Just put together a simple flood and drain system with one grow bed above my 33 gallon tank. I am trying to figure out how frequent should I start and stop my submersible pump over a day (24hours). Currently, I am running my pump for 1/2 an hour with a 3 hours interval to reduce noise and electricity consumption. I notice that my plants are not growing as much but they are nice and firm. The highest water point on the grow bed when the pump is on is just below the roots of my plants. About an inch of water remains in the grow bed when the pump stop pumping. My question is, am I doing this right?