[quote=JustOneMore20]Tetras are good for beginners. If you can find healthy Neons, they would be good. Lately though, people have been having issues with getting poor stock Neons.
By fancy fish do you mean Goldfish? Like fancy goldfish? If so, they are not schooling fish. Also, the can get pretty big and are a high waste producing fish (poop a lot), so you would be limited to 1 fancy Goldfish in a 20g. Or possibly fancy Guppies? They aren't necessarily schooling I don't think, but they enjoy the company of their own.
Yes, if the tank is large enough.
That is a good size tank to start out with.
For a 20g (assuming you get the "regular" version that is 24" long), 1 or 2 schools of fish would be fine, depending on what you choose. Obviously, some fish grow larger than other, but if you stick to small fish, you have room for 2 types. I personally think a school should be a minimum of 6 fish. Other people have their minimum's as well. The more the merrier. For a 20g, if you went with Neons and maybe another small schooler, you could have 6 of each. As for tankmates, small Corydoras catfish would be fine (look for Corydoras trilineatus or Corydoras panda). Those 2 species only get around 2 inches and are usually pretty common.
so i can get 6 of each of 2 schools,golden apple snails,and the cory fish? would all be find in a 20gallon?