I am looking into buying a 20 gallon aquarium and have decided on a bio wheel. Do i need extra aeration that the bio wheel does not provide or is it alright on its own?
Most power filters do a great job of water aeration, and bio-wheels probably do a better job than most of them.
If you have not had an aquarium for a long time or if this is your first, you may be thinking that you need an air pump to bubble air into the water. Although we used to do this to give our fish oxygen, we now know that it is not the bubbles but the surface agitation the bubbles create that moves oxygen into the water.
Personally, I'm not convinced on the whole bio wheel thing. As far as increasing o2 it shouldn't make a difference, its about surface agitation.
As mentioned earlier about the air bubbles thing, when they tested that, they bubbled pure co2, and the increase of o2 was the same as when they bubbled pure o2.
I have a 90 gallon tank with an under gravel evenflow power head 801 with a eheim canister filter 2217 or u can go cheaper a fluval canister they work the best for the price
The only advantage I can see with Biowheels (as far as biological filration goes) is if you want to replace your bio media often, and I don't know why anyone would want to. Biowheel or not, the bacteria colonies will grow to match the amount of waste. Perhaps there would be an advantage in tanks that are very overstocked - in that case I could see the extra surface area being an advantage. I'm sure they are great filters, but they do seem overhyped at times. Ok - don't mean to get too far off track here.
As long as there is adequate surface movement (which the Biowheel filter will provide), then there should be plenty of oxygen in the water. The Biowheel increases water-to-air contact, so it probably does provide a bit more oxygen than conventional power filters.