Two issues in this thread. First was the sand...why is you filter flow so strong that it stirs up the sand? What fish are in this tank?
On the enriched substrates, my experience to date (with Flourish) is not making me a believer.
First, I would not use these enriched substrates with corys or loaches, they are all fairly sharp. I knew Flourish was not as sharp as Eco-Complete when I felt them in the store, but now that I have the Flourish and was poking in some new plants earlier this week, I realized how sharp it is compared to my playsand and natural aquarium gravels. I've pulled my 6 corys out of this tank, they are now in "cory heaven" in the 115g with playsand, frolicking with the 30 other corys.
Second, it has only been 4 months but the plants are not doing much better in Flourite than they are in gravel or sand. I am dosing Flourish Comp in all tanks; I did discontinue Flourish for 3 weeks in the Flourite tank wondering if the substrate was sufficient, but plants started failing so I restarted the Flourish. Time will tell I suppose.
You certainly do not need substrate ferts (tabs or sticks) with an enriched substrate. Substrate rooted plants are the only ones that will benefit from either, and the enriched substrate should be sufficient in that respect. Using a liquid is still advisable as this will bet to the substrate plants but also benefit non-substrate plants, stem plants (that use their leaves and roots in the water column) and floating plants.