Alot depends on the fish you are stocking. Personally I tend to "overfilter" so I would be putting 2 of th filter that is one step below this one with the sponge filter. I *believe* you want a GPH
5 times the water in the aquarium since the numbers given on the box are for a filter running *empty* so no sponges etc. I am not a fan of bio wheels as I find they have a 50/50 chance of just stopping rotating for NO apparent reason.