Originally Posted by thekoimaiden
If you do go with guppies, get all males and no more than 3. Adding females to the bunch will guarantee babies, and a tank of that size can get overstocked very quickly.
I don't know much about apple snails, but I do know that they have a deceptively large bioload. They require a little more care than your average aquarium snail. I know there are some members here with a lot more experience with them, so maybe one of them will chime in.
If you're going to get an Apple Snail, make sure it's a Mystery Snail. I have kept them and I recommend them to people interested in raising snails. They will not eat living plants, are interesting to watch, clean your tank and won't grow too large.
Other breeds of Apple Snails WILL eat live plants and can grow to the size of a soft ball! I haven't heard of a Mystery Snail getting bigger than 2.5 inches.
Make sure you water is slight basic (above 7). Acidic water(below 7) will eat away at the snail's shell and eventually kill it. Also, check the hardness/softness of your water. Snails need calcium to grow their shells. If your water is very soft, you should raise the gh (general hardness). This will add more calcium and magnesium in the water so the snail can thrive.