Filtration, the flow of water through a material. Biological or otherwise to rid the water of impurities. There are two basic ways this is accomplished and four basic means to do it. First the two ways of filtering aquarium water.

The most common and best way to filter the water is to draw it out of the tank by means of a tube and pump system, allow this water to pass over different materials like cloth or Charcoal ( sometimes referred to as "Mediums") then returned by way of tubes or spill gate back to the aquarium. This way of filtration is found in three of the four basic types of filters.

The second way to filter water in the aquarium is to have a biological reaction within the gravel or "substrate" as it is referred to. Water is sucked from the tank, down through the rocks or gravel, under which lay slotted plates that allow the water to travel under the gravel and up lift tubes returning the water to the top of the tank. This is a very delicate filtration system and takes the proper care to make sure that it works as properly as it should.

There are many different types, brands, models of filters and filter accessories, I will cover the basic four types of filters in this article. Other filter types such as Sponge, Reverse UGF, and Fluidized Bed filters, etc. will be covered at a later time, or feel free to ask us at the club if you have questions on these other types now.

These four are the most commonly found in use in today's aquariums. The types are...
   Corner Filters
   Backpack Filters
   Under gravel Filters
   Exterior Canister Filters

Even though this is submerged in the tank, it acts like the first type of filtration I briefly discussed. It is normally powered by an outside air source. Air is introduced through the bottom of the filter drawing water with it through the filter by creating a vacuum. The water passes over cloth and charcoal then returns to the tank through an outlet normally located towards the top. These filters do not have a lot of flow through them so they are ideal for really small tanks, especially tanks with fry ( babies ) in them. These type filters are very inexpensive and require biweekly changes at least. Additional costs are incurred with an air pump, hose, activated charcoal and baton material.


This is the second and probably most commonly found filter in aquariums under 60 gallons in size. The backpack filter is powered by an electric pump drawing water up and out of the tank via a slotted tube. The water goes into a large well and passes through a cartridge of cottony material and charcoal, sometimes a sponge as well. Then the water drops over the spill gate and returns to the top of the tank. The flow rate on some models can be changed for lighter duty during feeding times and when you have very small fish that may get sucked up into the filter. Very neat and tidy filters, for biweekly maintenance, simply remove one filter and replace with another. This is more costly but less hassle than any other filter system. Some of these types of filters have "Bio-Wheels", these are rotating drums of pocketed material. The pockets allow for a bacterial growth that aids in killing off the bad waste in the water. This is very low maintenance, and I encourage their use.
Additional costs are cartridges, and the occasional impeller or tube when they break.

This Under Gravel Filter ( or UGF, as they are referred to ) is the most common filter found in toady's aquariums. The UGF is the second type of filtration that we discussed earlier in the page. As you can see in the photo, there is a slotted white plate, a covering of gravel or "substrate" and lift tubes towards the rear. These lift tubes either have an air stone and line inserted into them, the rising bubbles cause the water to circulate. Or the tubes have what is known as a "power head" attached to it. A power head is an electrical submerged pump the provides high water flows for larger tanks. This type filter is probably the easiest for the experienced hobbyist to maintain and the most difficult for the beginner. It requires patience when first starting out, something most beginning hobbyists usually do not have.
The UGF draws the water down from the tank, through the gravel where the fish waste material gets trapped and broken down by enzymes. The water flows under the gravel in a cavity that the plates have provided, up the tubes and out into the tank. If a power head is used a great current is introduced into the tank, which direction and rate of flow can usually be directed. Additional costs are gravel, air pump or power head ( most likely a combination of both ) lift tube filter caps ( this is the black area you see at the top of the tube ) in charcoal or another material depending on what the water conditions requires.

Click here for actual set up instructions

The canister type of filtration is the least visible and most expensive type of filtration for the general hobbyist. Some canisters also allow the hobbyist to decide what type of filter medium as well as just how much of it he/she wants to use. Other canisters have pre-manufactured filters and medium packs that you can purchase individually or in larger more economical packs.

I really like the simplicity behind the canister filters, I also appreciate the fact that they are the least intrusive to the aquarium. The down side to canister filters is the cost. Canister filters usually run 3 to 10 times the cost of most other types of filters. The canister filter is very basic, a freestanding unit on your floor plugged into the wall. Two tubes, one an intake the other a return, flow between the tank and the filter. A simple electric motor keeps the whole thing going. Additional costs can be filter packs, medium, tubing and the occasional impeller.