Just like anarcharis planted or floating does well gravel will workI might try to get some from the river. Does it need substrate other than gravel or would that work?
Would be good for forest. I find the best way for plants is by trial and error, unless your dedicated to a planted tank. I'd say most are marginal that do better just roots in water but it's hard telling may not have gotten enough nutrients? If the plant doesn't rot it's probably ok may not see great growth without ferts/CO2 . A plant guide will tell you what defeciences cause your plant to turn yellow, etcI had some plants in there before but they were sparce and taken from the river they didn't die but they didn't thrive either and the fish left them alone. I want a small forest on one side of the tank for the smaller fish to have some cover. It's also for my sunfish tank.
Shouldn't need root tabs you can add them but you'll have to watch algae growth as if watts per gallon isn't enough for plant maybe CO2 isn't enough where algae growth will overtake plant uptake of nutrients ie tabs if that made sense also overstocking isn't necessarily bad with plants as they add nitrates CO2What about anacharis or hornwort?