What Is the Best Homemade Filter for Fish Tanks?

There are many different ways to build a filter for a freshwater or saltwater aquarium system, but there are some general guidelines to follow for making the filter as effective as possible. Aquarium filters and filtration systems should remove large particulate matter, organic compounds and chemicals, biological contaminates (such as parasites and diseases), and some undesirable inorganic chemicals. The best filter will do as many of these things as possible, although cost may be a concern.

  1. Removal of Large Particles

    • The largest particulate wastes (detritus) typically found in a freshwater or saltwater aquarium are uneaten food, fish excrement, pieces of plants and algae, and occasionally dead animals. Detritus is easily captured by mesh filters such as those made from nylon or cotton. The greater the surface area of the filter, the more detritus it can capture before it needs to be cleaned or replaced. Include a large detritus filter in your homemade filter design.

    Dissolved Organic Compounds

    • Granular activated carbon (GAC) is one of the best mediums to use for removing dissolved organic compounds and some chemicals. GAC is widely used for water filtration and purification and is available at most aquarium stores and online. For a homemade filter, fill a nylon bag with a few tablespoons of GAC and allow the water to pass through it. Saltwater aquariums also make use of a protein skimmer to remove dissolved organic compounds. Skimmers work by mixing air bubbles with water and collecting the bubbles in a cup at the top of the filter. They are very effective for saltwater aquariums.

    Chemical Filtration

    • Certain chemicals build up in the aquarium system over time and must be removed. Replacing some of the aquarium water with freshly prepared water removes most of these chemicals; however, there are some filtration methods that can help. The fish in both freshwater and saltwater aquariums excrete ammonia, which is very toxic. Although the aquarium can usually remove ammonia through a process called the nitrogen cycle, some aquarists add bioballs or deep sand beds to their filtration systems to help the cycle along. Bioballs are most often used with freshwater aquariums and are simply plastic or ceramic balls with increased surface area. They help convert ammonia into nitrite then into nitrate, which is less toxic to the fish. Deep sand beds are used in saltwater aquariums to help reduce nitrate and are simply a 4- to 5-inch-deep sand bed either in the aquarium itself or in the filtration system.

    Biological Sterilization

    • Some aquarists take an extra step in protecting the aquarium inhabitants from diseases, parasites and nuisance algae by incorporating an ultraviolet (UV) sterilizer. Water passes by a UV bulb and the ultraviolet light kills any microorganisms in the water. UV sterilizers kill beneficial organisms as well, and not all aquarists employ them in their filtration systems.

    Removal of Inorganic Compounds

    • Unless you use reverse osmosis or distilled water, inorganic chemicals like aluminum, copper, phosphate, lead and mercury can build up in the aquarium water. Most of the time there will be just a trace amount of these compounds in the water and they do not pose a danger to the aquarium inhabitants. Some companies make special filter media to remove things like phosphate and aluminum, but many aquarists turn to plants, macroalgae, and mangroves. Plants and algae take up dissolved phosphate and mangroves are known to draw heavy metals from the water and substrate. If possible, include these in your filtration system.