By Carl Strohmeyer
There is a lot of information about bio wheels and their importance in bio filtration in aquariums. In theory they are great idea and bought into this idea for years without testing the results to see if the hype was true. In theory the wheel turns into the air where oxygen the aerobic bacteria need to remove ammonia and nitrites is much more abundant. But after many a wheel stalling with the many customers I serviced aquariums for I decided to start testing these wheels vs. other bio filter methods.
I removed the bio wheel on penguin filters on comparable aquariums with comparable bio loads and fish and found no discernable ammonia spike. Yet when HOB filters that had running Sponge Pre Filters attached to their intakes were removed, there were discernable ammonia spikes. This is not to say a bio wheel does not work at all, especially there is less build up deposits on the bio wheel fiber.
What is much more important is to have an adequate amount of dissolved oxygen through agitation of the water surface which is where oxygen and other gasses are exchanged from the atmosphere and the aquarium. This is also important for the aquarium Redox not just the aerobic bacteria. I have found a porous sponge filter media to maintain more bacteria in well oxygenated water.
Here are a few reasons behind the poor results of bio wheels: Hard water buildup; although not as much a problem in soft water aquariums, this is a major problem with hard water aquariums and especially marine aquariums (where these bio wheels are a total waste of money). What happens is the calcium, salts and other deposits form in the pores of the bio wheel fiber, not allowing bacteria to form there. This is the main reason for the lack of effectiveness for bio wheels. My tests in Discus aquariums (which are soft water) showed better results for bio wheels (although not as well as sponge or other porous media).  Lack of surface area; a bio wheel does not have the surface are of many other bio media products from sponge media to the very porous pumice media used by Eheim and others.  Bio wheel stalls; bio wheels have a bad habit of stalling. This is only a minor reason to not have these bio wheels as this is a correctable problem.
Here is a way correct this problem (this will be an on going maintenance problem). Make sure the Teflon ends on the bio wheel axle are clean and have no build ups of calcium you can replace these with Teflon tape in a pinch. Also make sure the bio wheel assembly is not to tight, simply remove the bio wheel and gently stretch the assembly apart so the wheel can spin more freely.
The aquarium hobby is ripe with anecdotal aquarium information and advice however these theories although based in sound principles are rarely tested. For more about this subject please visit my Aquarium Answers Blog: Aquarium Answers; Do Bio Wheels really work?
By Carl Strohmeyer
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