i agree with the posts above. the general rule for tanks is about 1 inch of fish for 1 gallon. so neons getting around 1 inch, you could have about 10 , or a smaller group of 5,6,7, and some corries or something to keep the bottom of the tank cleaner. I hope this helps .
note. the rule has exceptions like, there is no way 1, 10inch fish, could live in a ten gallon, but i'm sure you knew that but it's amasing to see the people and their poor fish that don't.