Well let's say that you get neon tetras, the might be stressed at first because they don't know the tank and then they will have something chasing them sometimes. Could you post a pic of your tank. As of other fish you can get: cory cats, neon/cardinal tetras (careful because they are sometimes known for nipping fins), fresh water shrimp, african dwarf frogs, rasboras, lamplight tetras are good, and platys (they are live-bearers so if you don't get all males/ females you might have babies). Those are just some that I know that will work. A guide, not a definite guide, is no long flowy fins like guppies, streamline fish like tetras that can swim fast. Some fish like tetras need to kept in groups of about 5 or more because they are schooling fish. Hope this helps.
15 Gallon NPT
1g no tech bowl in the making