well yes, I think you should add in a biowheel. However, it may not be necessary because good bacterial growth should be in your decor, gravel etc...but to be sure about and for higher sucess in combating ammonia to turn into harmless nitrate I believe a biowheel is a very good investment. Now, you can't have just the biowheel, you'll have to keep the filter in it because that is for the chemical, biological, and something else cleaning so the filter is very important, basically your filter cleans the crap out of your water, and also the harmful chemicals in your tapwater, of course before doing water changes, you need to have a water conditioner to further take out the harmful additives put in water. Ok i hope this enlightened you on your question.
RacerFish