If it's true that plants prefer NH4+ and need to expend energy converting nitrate to NH4+ before using it, and they take in NH4+ faster than they will the same amount of nitrate, would it not make sense to have as little biological filtration as possible on a planted tank - thus making more of the nitrogen available to the plants as NH4+ instead of the plants competing with the biological filtration for NH4+ and then having to resort to nitrate for their needs? Would this result in faster growth? On a low tech tank, of course, since we wouldn't want to have to fertilize NH4+ due to the algae issues it may present.