The site is worse than useless when it comes to giving advice. One reason is because it tries to equate filter capacity with fish capacity.
Let's get down to basics. No filter ever removes anything from a tank. It merely stores particulate and provides a place for biofilter bacteria to grow. Any filter that is anywhere near big enough for a given tank size has more than enough bacterial colony capacity for a tank twice as big. The limiting factor when stocking has nothing to do with the filter and everything to do with the tank's oxygen capacity based on the surface area and depends on the way that the fish relate to each other. If the fish cannot get along, a 100 gallon tank is too small for two moderately small fish. The factor that many think of in terms of stocking levels and filters is often the ability to deal with ammonia, which is totally meaningless. I can and do filter a 20 gallon heavily stocked tank with nothing more than a simple sponge filter. The important parameter, as far as chemical problems in a tank, is how much waste a fish produces compared to the amount of water you replace with water changes. If you are willing to do more and larger water changes, you can keep more healthy fish than if you are lazy about water changes. In that sense, the filter size can cause you problems rather than prevent them because it makes the water look cleaner while the chemistry goes to pot completely.
. Which is fine.......if it's true?
