I believe this depends who you ask, for the most part though i hear that you should have at least 5 gallons for mystery snail and betta. Snails poop a lot, and so you need a tank that can support that bioload.
EDIT: i forgot to add that instead of adding anymore fish or snails or anything you could add a moss ball. They are not quite as active as a fish or snail, but they do follow light. In the mornings when i turn on my light they float to the top of my tank and will hover there for a while.
Last edited by Loralyn94; 08-08-2011 at 01:22 AM.