i have seen many aquariums that most of the people on here would say they are overstocked. these aquariums belong to people who have been doing this for years. your opions are great, however some people don't know what they are talking about. you would be surprised of what types of fish can be kept together and be healthy and happy. i think anything is possible. i would consider overstocked if you had a 30 gallon with 30 fish overstocked. i feel that as long as you are reasonible and have good filtration, anything is possible.