I see that they sell Black Japanese Trapdoor Snails for ponds, and say they are great for algae cleanup. I have also read on this site about snails being a nuisance, and taking over one's aquarium. So I am a little concerned about getting snails. Does anyone have any experience with them?

If they are good, I would like to get some and quarantine them for now. And I would have to start from scratch in learning how to care for them. But I do have a few empty tanks, and they look so ... empty!

Well, I did some research on those snails, since the only variety I have ever seen are those little pesky ones, where you introduce a couple of snails, and you turn around once, and literally have 100s.

Apparently, the japanese trapdoor snail isn't one of them - it isn't egg laying, and only produces youngens twice a year in manageable numbers. They are quite hardy, can withstand some cold weather, and seems to be leaving live plants alone. "Seems to be", as in "you never know"...

Here is the whole article about them...
"The shell of the Japanese Trapdoor Snail, also known as the Chinese Mystery Snail, can vary significantly in color and pattern, but is usually brown to gray. It originates from ponds and slow-moving streams with some vegetation and a muddy substrate. The Japanese Trapdoor Snail bears live young generally twice a year, and limits the number of young to just a few. Thus the number of young produced is less than egg-laying snails, which is beneficial since some snails may overrun ponds or large aquariums. It will eat algae and generally does not eat live plants. This, too, makes it a good addition to smaller ponds where it can aid in controlling algae growth. It is an omnivore, and should be fed algae, vegetables, fish food, frozen foods, and live food."