How big are your fish and how much do you feed and siphon the gravel?So to answer some of those many questions, I have a 40 gallon breeder. Stocked with 1 green sev, 2 German blue rams, 1 Plecostomus, and 3 pygmy Cories.
I have a Marineland Penguin BIO-Wheel filter. Model 200, for up to 50 gallons. Maybe I should get the next one up then??
As far as biological filtration no one that has actually researched it disagrees that the more media you have the better and the more well oxygenated the media the better. Though there are several different filtration/media types, a biowheel is a good biological media due to the fact that it provides plenty of oxygenation and can provide sufficient surface area, but the one small biowheel you have may not have enough surface area to grow sufficient bacterial colonies for your bioload.The problem I'm running in to, and have been since I started this hobby is that everyone has their "own opinion." And having so many opinions that are different isn't really making it better.
Researching biological bacteria and how they function and thrive is by far the most important information you can learn in maintaining a healthy aquarium. You basically have a small sewage treatment plant on your tank (your filter) and if it's not functioning properly then your fish are living in their own toxic waste.