DIY Aquarium Canister Filter

Canister filters are a good way to add powerful filtration to your aquarium without adding extra equipment inside the tank. Canisters eliminate the need to hide large in-tank filters and are a good option for a planted tank. The outlet can be set to avoid surface tensions unlike a more traditional hang-on back-power filter or air-bubble filter.

  1. Canister Filter Basics

    • A canister filter is an airtight and waterproof reservoir that holds a pump and various layers of filter media. It usually sits below the tank lower than the water level. The water is drawn in through an intake tube, run through the filter layers, then expelled through an output tube back into the aquarium. Canister filters can contain any type of neutral media that provides surface area for beneficial bacteria to grow on. Popular options include lava rock, chunks of ceramic, or any other porous material that will not decay and has a large surface area. In addition to biological filtration, the cansisters often contain activated carbon to remove chemical impurities in the water. Mechanical filtration for larger pieces of waste is usually done with an intake strainer on the end of the intake pipe.

    Plumbing and Pumps

    • An inline submersible pump can be mounted in the bottom of the reservoir container to either pull or push the water through the plumbing. Pumps are rated by gallons per hour. A good circulation rate is at least three to four times the volume of the aquarium every hour, minimum. Make sure to calculate the flow rate of the pump, including the head, when deciding which pump to buy. Depending on volume of water flow, common 1/2-inch to 1-inch PVC pipes and fittings, along with vinyl tubing, are acceptable for the plumbing. Make sure all PVC cement has completely dried and cured for 24 hours before running water through it. Chemical residue can harm the fish.

    Biological Filtration

    • The goal with biological filtration is surface area and water movement. When deciding on what type of filter media to use, think of what provides the greatest surface area but does not inhibit water flow. A popular DIY media is the nylon mesh skin exfoliaters sold in the health and beauty section of most stores. If you untie the center knot of an unused one and unravel the mesh, this is a perfect neutral surface area for bacteria to grow on--and they are very inexpensive.

    Extras

    • When building a filter consider, adding on extras that are commonly found in many manufactured filters. Some include an inline heater or UV sterilizer. Consider including a space for those where water will flow through easily, after it has been filtered. Many models of CO2 reactors are made to attach inline with the canister and run off the same pump. Adding any of these to your canister filter will eliminate the need to add this equipment inside your tank or to run extra pumps, leaving more room for fish and plants and saving energy.