Well I just got back from the pet store and the guy there told me that only goldfish would go with betta's, but not tetras, guppies etc because betta's are cold water and so wouldn't go with tropical fish.
This is why I ask questions here, people at pet stores never seem to know what they are talking about!
I ended up getting 4 neon tetras and some plants to start the tank off (this is my first heated fish community so I wanted hardy fish until I get better at fish keeping). Actually I got far too many plants and will have to throw some out, guess I overestimated the size of a 10 gallon, whoops
Does having a lot of plants make the water cleaner and allow for more fish, or do they allow for less fish because they take up space?