Canister and hang on filters

If I am not mistaken, canister filters provide better bio filtration, and most of the time they are used on tanks 20 gallons or more. Some people use them on smaller tanks. They don't have to have as high of a flow rate because they have more media and can handle the crud. I prefer HOB filters, because that is what I started with and I am used to maintaining them. By what I hear, canister filters don't have to have as much maintenance required to the impeller. This is true to some point, but HOB filters are easier to clean, IMHO. My Whisper filter doesn't have to have the impeller cleand but about once every 6-12 months.

I also like the HOB filters, I like Aquaclear now because they are cheap in price, do a good job of cleaning the water and have the foam inserts that you can rinse time and time again. You dont have to keep buying the bio bags. In the long run the Aquaclears are cheaper to maintain. I also add a little filter floss between the foam inserts to help trap smaller debris. There are alot of diferent options for media with these. I have also never had any problems with them.

Canister filters do hold more media than the hang on back filters but it has been said by some that there is a possibility that the bacteria in the uper levels of these filters will never have sufficiant oxygen to thrive because bytime the water reaches the uper level of media in them the oxygen is probably pretty well used up by the bacteria in the lower level of the filter.