I just set up a new tank with Flourite for substrate (1/2 - 1" layer of sand on top) and am wondering if I should add Jobe's spikes for ferns. I added them in my last plant tank (with soil substrate) and the sword, crypts and apons. all took off. Will I need the Jobe's for the N-P-K? Jason Miller Sherwood Park, AB - getting the planted tank bug!