I currently have 5 snails (one is really really small), one betta fish, 6 neon tetras, 3 cory cats, and one shrimp in my 10g filtered, heated, and lighted tank. There's also 5 plants. One thing about the snails: they're wild. My dad caught them for me in the marsh (I live in Louisiana). So I'm not sure of their species but I was reading around and learned that "periwinkles" are pretty common snails:
http://en.wikipedia.org/wiki/Common_periwinkle Maybe that's what they are?
I change the water by 50% every week. Should I work on a different cleaning schedule and amount?
So is this too much? I don't plan on adding anymore fish or other little creatures until I upgrade my tank.
And speaking of upgrading, what do you guys I suggest I upgrade to?

I was thinking around a 50g or 75g, or is that too much of a leap? :P