Godbud, it is OK for the taproot to be constantly in the water in the beginning. In fact you want some of it to be covered. But once it is about the age and health of yours, it should have a bigger root structure, and this is the time to start feeding more and watering less. You want to water/feed at little as possible for the duration of the grow. The more the roots can breath oxygen the better. I pretty much go by the PPM schedule I linked above.

Hope that helps a little.