While I had to spend money to get the fish and plants, Kingdom Mollusca came along for free. Within a few days of getting plants, I started to see snails in the tank. First one, then another, then a third. I also saw what appeared to be snail eggs (although the most exposed ones soon became Cory food).
After two weeks there's a large - and well-established - snail population going. And there's some decent species diversity - while I know almost nothing about snail identification (or even where the species are from), there are several distinct shell morphologies, including one with a largely translucent shell. With hard water and a high pH I'm sure the snails are happy enough. And while there isn't any algae to speak of in the tank (yet), there are enough plants (and, presumably, epiphylls) to keep them alive. Of course, the plants that brought in snails could have brought in all sorts of other parasites...we'll see how it goes. For the time being there's nothing that eats the snails, so a population explosion is very likely. Of course, I really want Angels...who are moderate molluscivores. Still, I doubt any casual snail eater will really be much good at managing the snail population.