Aquarium Undergravel Filter

The undergravel filter is considered by many to be the most effective type of filter because it provides a high level of biological filtration. This filter consists of a plastic plate that sits under the gravel of the tank. Water is drawn through the gravel by pumping air to the bottom of the filter with an external air pump. Some undergravel filters are driven by powerheads mounted on the intake tubes. Both kinds provide excellent water circulation and aeration.

In essence, this filter uses the aquarium gravel itself as the filter media. Thus, very little mechanical filtration is involved and chemical filtration is completely lacking. The undergravel filter relies chiefly on the establishment of a healthy bacterial colony in the gravel. For this reason, certain kinds of gravel are required for this filter, and a longer setup time of many weeks is necessary to establish bacterial colonies. However, once a healthy filtration system is established, this filter can be used for months without intense maintenance and cleaning.

Although this system provides the most valuable kind of filtration, it may be the most complicated for the beginner. Excessive debris in the aquarium can clog the filter bed and must be routinely removed. Aquarists who want to maintain live plants will find that this filter will destroy root systems. In addition, fish may disturb the substrate and upset the filtration bed. The novice would be better off with an external power filter.

Aquarium External Canister Filter

The external canister filter is the next step up in power filters. This filter is much larger than the others and is designed to filter large tanks of 50 gallons or more. The canister filter is composed of a large jarlike canister, which generally sits next to the tank. It contains filter media and activated carbon, like the other filters, but has a much more powerful motor for filtering large amounts of water. Water is drawn up by an intake suction line and sent back to the aquarium through a return line. If the return line is properly positioned, water circulation can be provided by these filters. I only recommend this kind of filter for the aquarist with a larger tank.

Aquarium External Power Filter

The external power filter is the easiest and least complicated filter system for the beginner’s aquarium. These filters provide all three kinds of filtration and are specifically designed to turn over large amounts of water. The external power filter hangs on the side of the tank and is powered by its own motor. Water is drawn into the filter by a U-shaped siphon tube. it passes over layers of fibrous filter material and activated carbon and is returned to the tank via a gravity trickle system or a return pipe. Like the box filter, the power filter circulates the water, providing aeration.

While it works on the same premise as the box filter, the power filter is much more efficient at removing waste and debris from the tank. It does not need to be cleaned as frequently as the box filter. Many models have special filter cartridges that make cleaning these filters extremely easy. In addition, various types of cartridges can be purchased to chemically alter water quality and correct water chemistry problems.

Aquarium Internal Box Filter

As the name implies, the internal box filter sits inside the aquarium. An external air pump drives air through the box, drawing water from the aquarium through fibrous filter media and activated charcoal. Layers of filter media provide mechanical and chemical filtration, as well as adequate substrate for biological filtration. Since it is driven by air, this filter circulates and aerates the water.

In my opinion, the box filter does not provide adequate levels of filtration for the average aquarium. Aquarists who start with a tank of 20 gallons or more should not use this type of filter system. It is simply too small to handle the waste and debris that accumulate in the tank, and it has to be cleaned frequently.

Aquarium Air Hose

Your air pump and airstones require an air hose to link the two. This is plastic tubing that delivers air from your pump to the airstone. This should fit snugly at all joints so air does not escape from the system. Air leaks reduce the efficiency of the system (filter and airstone) and may ultimately burn out the pump. Make sure the tubing is manufactured for use in an aquarium; other grades may be toxic to fish.

If you intend to run multiple airstones or additional devices, such as filters, from a single pump, you need one or more air valves. These enable airflow to be directed to multiple devices from a single pump. Using several air valves enables you to turn devices on and off as you like.

Aquarium Airstones

An airstone is generally made of porous rock that allows air to pass through it, splitting the airstream into tiny bubbles. Too fine a mist will cause bubbles to adhere to various tank decorations and to fish. You want the bubbles to slowly travel to the surface and agitate the water. Commercially manufactured tank decorations that act as airstones can be purchased at almost any aquarium supply store.

Aquarium Air Pumps

There are two general air pump designs: the diaphragm type and the piston type. The former is much more common and generally provides enough maintenance–free use for the beginner’s aquarium. The piston pump, however, is more powerful and should be used in larger aquariums, particularly if an undergravel filter and multiple airstones need to be powered. The size and power output of air pumps vary. Consult your local dealer to match your aquarium with the proper air pump.