planted tank substrates
one of my low light tanks started out with only fish poop and seachem root tabs for fertilizers, and i had phenomenal growth even though i was barely above 1 WPG. this went great for a few months until the tabs ran out, and growth basically came to a dead halt, with no perceivable movement. at that point, the only fertilizers were from a half stocked tank of fish. hoping to rectify the issue, i swapped out the bare gravel for eco-complete in the hopes that i could get something near what i had before. i had a 2 inch thick covering of eco complete... and nothing. they didnt grow much at all and it was basically the same as when i had bare gravel. i've since started adding liquid ferts to the water column and growth has picked up, although it is still nowhere near what i had with the root tabs.
for my next planted tank, i think i'll try soils since having an excellent substrate seems to be a key to running a low light planted tank. this has been my first experience with special plant substrates which are enriched with nutrients beneficial to plant growth. my question is, is my experience typical of such substrates? if not, what could be causing this? are other widely available products like flourite better? what about high quality substrates like ADA's aqua soil? or garden soil?