If you are just starting with a new set up you want to have only a few fish to start. Let the nitrites and nitrates settle in and let the good stuff grow before introducing too many fish at once. Once your tank is established you may want to add a few more and eventually, if you have good filtration as mentioned above, you may be able to add 10 neons. Water changes are important and be sure not to over feed the fish. Maybe you already know these things lol. Be sure to test the water in the first few months to make sure things are stable.