I wouldn't keep your betta with any other fish in a such a small tank. Even with a snail he might get aggresive and kill it.

Plecos are a huge help in keeping the tank clean. I had a common pleco (found at most petstores) but it got huge, 11". Now he lives in a 75 gallon tank which is just his size.

Good luck with your fish!

AquaSafe is a good brand of dechlorinator (sp?). You can find it at almost every petstore, and some pet departments at Walmart and Target even have it.