I would not mess with Flourite. I used this in my 70g and after two full years saw absolutely no benefit to plant growth compared to my six other tanks with fine gravel or play sand, and the same plant species and lighting, etc. Waste of money in my view. As Eco-complete is much the same product, I would not go with that either. Another aspect is the roughness of both products; substrate fish like corys and loaches can have isues. I had to move my corys out due to mouth injuries, and there is no doubt that it was the substrate (Flourite). I had chosen Flourite over Eco-complete after a catfish breeder warned me off the latter, as I though Flourite was smoother in my hand, but not so obviously.
Sand is probably your best substrate choice, depending upon intended fish species. Liquid fertilization is all you need. Other types of enriched substrate that I have not tried (like the ADA, etc) may or may not have benefits in high-tech systems. But the truth is that plants will grow in most any substrate provided light and nutrients are present in the aquarium.
I tore down my 70g after two years, and put in play sand. Now, one year later, the plants are thriving better than before, and I can have corys again in this tank. And the $15 for two bags of play sand compared to $180 for Flourite is a nice plus.
Byron.