Keep an eye out on the snails, they reproduce like rabbits. I have a 30 gallon in which I had the same thing happen as you. I have no live plants tho. But, I left them in there and recently got rid of the fish in there and now notice- two months ago I saw 2 snails, now I have about 30. The snails in my tank have more cone looking shells, but I'm fairly certain most snails reproduce rapidly. As long as they are not eating your plants, I would leave them, just keep an eye that they don't get out of control.