I agree that that is drastic. You could keep your betta with an apple snail for a few weeks-months in a 2.5 but param readings would get high fast and considering that (on rare occasion if the snail lives long enough) apples can get to the size of baseballs, a 5 or even 10 gal would be in your future. A nerite would do very well in a 2.5 gal as they stay small.
Ramshorns are asexual, a single one can reproduce at will. They are bred by at home aquarists for feeders for puffers sometimes as they are very easy to propagate. You would quickly have a lot of snails and a lot of bioload.
Last edited by Artemis; 04-13-2013 at 10:12 PM.