I recently purchased some Jobes fern spikes and put a couple broken up under my plants in my five gal. I also have a planted twenty gal., but it has a UGF. The point of using the spikes is to keep the nutrients in the substrate, but w/ a UGF, would all of the nutrients just dissolve into the water column (I already use Flourish and Flourish Iron). Thanks Jason Miller Sherwood Park, AB (780) 464-9635