I have been a participant in the hobby of Aquariums for twenty-five years. In that time I have done both freshwater and saltwater tanks. I have had the opportunity to try many different types of filters. The one that has out-shined them all is called the H.O.T. Magnum. It is a hang on the back of the tank canister filter. This filter has a superior design because it has the ability to accept accessories that increase its efficiency. The filter in its base form provides mechanical filtration. It is able to hold a large quantity of activated carbon. This enables it to be used on larger tanks up to fifty-five gallons. There is a sponge pre-filter sleeve that wraps around the carbon container. This collects any debris that comes into the filter. Earlier I spoke about the ability to add accessories. Marineland Products makes what is called a Bio-Wheel, this provides biological filtration that is vital to a healthy aquarium. The Bio-Wheel harbors good bacteria that take ammonia that is given off by decaying waste and turn it into what are called Nitrites. Another bacteria also present on the Bio-Wheel take the Nitrites and turn them into Nitrates. Nitrates are removed during water changes and are far less harmful to your aquatic life than ammonia. On my fifty-five gallon I have a H.O.T. Magnum with a Bio-Wheel 60 attached. This set-up keeps my water gin clear and ammonia free. One of the best features of the H.O.T. Magnum is the Micron filter. You can switch out the carbon container and insert the fluted micron filter. It will filter out particles that are larger than a micron. That is so small that this filter can effectively filter out water carried parasites like, Ick, Velvet and many other diseases that strike your fish. This filter averages $89.00 but, it is worth every penny. All parts are available from the company, they last a long time. I have several of these and one is fifteen years old. The good designs are the ones that stand the test of time. I recommend this filter even for the person who is just starting out with a twenty gallon tank. The filter will keep your tank cleaner than any other and it will help you not have to face some of the things that can happen early on in the hobby that might discourage you from continuing. This filter is like a box of success in the aquarium hobby.