hey chickadee... there was a few times, back when I had a five gallon, that I would empty the tank out and wash it with soap and rinse it a bunch of times before I set it up again... then I'd have those snails come back... somehow they would survive my rigorous cleaning... something like hornwort might help.. plants like that do better when they are floating, at least for me because I also don't have much light.. instead of trying to root them I usually just drop them in and let them be where they want to be... when they float at the surface they grow a lot better for me... another option is plant bulbs from walmart or somewhere. They aren't great, might not even do great for you, but they are cheap... it's less than three dollars for 4-6 plants, if they all grow... that might help a little anyway. and I've never done anything special for substrate for any of those things... of course I don't clean my gravel as often as I should... I'd start with some hornwort... there's a good chance you would pick up a few new snails with the purchase too... oh yeah, another option would be to setup something small, doesn't really even need to be a tank, with some filtration or aeration and leave it alone, with a plant... this is just my opinion, something I myself would do and don't think I'd fail, get something like a large vase or something that's around 1-5 gallons, add an airstone and a plant, place near a window and let it be for a while... with snails of course, you'd have eggs in no time... lots of them... well, experiment anyway, I'm sure you'll find something that works for you...