I'll figure I could update you all. A month ago I set up my 20 gallon tank with play sand. I have a coralife lighting fixture equiped for two 65 watt 10K bulbs although I am only using one... don't know if I really need to add a second one with the same specs.
I am adding 8 ppm (I know, very low...) of CO2 via a DIY reactor connected to my Aqua Clear 200 (soon to be replaced by a Dupla diffuser) and have added Seachem Flourish tabs to the sandy substrate.
I have planted several species; Rotala macrandra, Rotala indica, Cardamine lyrata, Ludwigia peruensis, Ludwigia broadleaf, Red Myriophyllum, Green Myriophyllum, Alternanthera rosefolia, Echinodorus tenellus, Glossos, Aponogeton ulvaceus and a couple of crypts. Of all those, the casualties have been the Alternanthera and the Red Myriophyllum. The rest are showing various degrees of development but overall I do have to say they are doing very good. Most of them pearl every evening; even the tiny glossos... amazing!
So... yes, sand does work. If I can get the CO2 to diffuse better, I am sure I'll be able to have even better results.
This is not my first planted tank but it is the first with sand and the first time I actually add CO2 and I do have to say the difference (because of the CO2) is remarkable.