Well... Fasilitor from Aptos was the first product I used. It was kinda weird, its a gell and needs to be mixed in a seperate container with pure water before putting it in your res. If you dont do this chunks will remain after you add it. It works great. I had foam issues for a couple days but my air pump is a bit of a monster, so i can't say if you will have this problem. Power Si was designed by the same person that did Fasilitor, but its cheaper. There are 2 Power Si one for bloom, which kinda sucks, but it is what it is. If you choose to run just one of these products pick the non bloom version. It makes more sense to give them silica from the beginning, Power Si also advertises that it will slow verticle growth of a lanky sativa if you double the dose. I dont know if there are any other ramifications in doing that, longer flower, etc. But it didnt slow shit on my last grow... for the record I didn't double the dose though. Both Fasilitor and Power Si are meant for hydro, but ive read works just fine in other media. I usually grow 1 in dirt the rest in hydro. My dirt plant that was usually fed with hydro water did 10oz last season