Nature Aquarium Filtration

A filter is used to remove unnecessary substances contained in the water of an aquarium. It is not exaggeration to say whether the beautiful aquascape of Nature Aquarium can be maintained in a good condition or not depends on the filter. This article explores biological filtration, which is the most important filtration method, through an experiment.

Three filtration methods

The amount of water in a typical Nature Aquarium tank is like a puddle in nature. Since a large amount of aquatic plants and fish that are unthinkable in nature are housed in such a small aquarium, the water must be purified artificially. A filtration system does this job. Although it is artificial, the ideal filtration system for Nature Aquarium is the type that utilizes the mechanism that also exists in nature in which microorganisms can work effectively. The filtration that takes place in a filter is largely divided into the following three types. The first one is the mechanical filtration that captures relatively large particles with fine filter media. The second one is chemical filtration (adsorption filtration) by which substances are attached to the surface of filter media that has fine pores on the surface and thereby offers a very large surface area. The third one is biological filtration that decomposes organic materials in water with the help of various microorganisms that colonize filter media. Whether an aquascape can be maintained beautifully or not depends on how well this biological filter functions.

The importance of a biological filter

Ammonia that is generated from fish waste and dead leaves of aquatic plants is highly toxic. In high enough concentration, fish and shrimp are poisoned and killed. Nitrifying bacteria multiply in a filter and convert toxic ammonia to nitrite (NO2) and then to non-toxic nitrate (NO3). Thus organic matter is converted to inorganic matter and the water is purified. Not only bacteria but also a large number of protozoa colonize filter media. Protozoa mainly pray on bacteria and other protozoa. For example, if disease-causing bacteria that infect fish try to multiply, as long as the filter is functioning well, they are eaten by protozoa and the rate of disease outbreak is reduced. The microorganisms in a filter play an important role in natural ecosystems as well. They are the “decomposers” at the bottom of the ecosystem pyramid. A biological filter is an important part of Nature Aquarium that supports its basic concept of a small ecosystem where fish, aquatic plants, and microorganisms coexist and its environment is stabilized through a system similar to the one in nature.

Experiment

We conducted an experiment by setting up actual aquariums. New aquatic plant aquariums were set up with filters using different media. The graphs on the left show the changes in water quality. A standard Super Jet Filter ES-600 comes with anthracite and Bio Cube (Media A). Anthracite removes excess nutrients in the water with its excellent adsorption ability. Sponge type filter media Bio Cube works as a mechanical and biological filter. It is also the raw material of Bio Rio (Media B). ADA’s product Bio Rio is seeded with dormant filter bacteria. In this experiment its base material was used as-is. Media C (called activated Bio Rio) is also Bio Rio, but it has been in use in an aquatic plant aquarium and therefore it was already colonized with bacteria and protozoa. The changes in water quality were measured after the aquariums were set up with the three different media (A through C.) Ammonia is normally the first thing that shows up after setting up an aquarium. Ammonia decreased in the aquarium with Media A faster than in the other aquariums. This is most likely due to the adsorption ability of anthracite. NO2, which was converted from ammonia by filter bacteria, shows up next. It also decreases the fastest in the aquarium with Media A than in the other two aquariums. It is probably due to the adsorption filtration. However, in terms of NO2 concentration, the aquarium with Media C had the lowest concentration. This seems to be due to the fact that NO2 was quickly converted to NO3 with the biological filtration which was active from the start. In the aquarium with Media B, the microbes in the filter were not fully developed and it took more time for the NO2 to disappear. As for the reason for NO3 that existed from the beginning, it may be contained in Aqua Soil Amazonia and Power Sand in the substrate. As in the case of NO2, its concentration did not rise much in the aquarium with Media C. In fact, it started decreasing much sooner. It is necessary to repeat somewhat large water changes normally to reduce NO3 rapidly. However, out of the three aquariums, the aquarium with Media C with activated Bio Rio had clear water from the beginning and aquatic plants started to grow fast. Nitrogen in ammonia, NO2, and NO3 were absorbed by aquatic plants as nutrients in the aquarium with Media C where the water condition is good and aquatic plants started growing fast. Although they also decreased in the other aquariums later, the fast rate of decrease and the low concentration in the aquarium with Media C was characteristic of the aquarium.

<Common Data>
Aquarium: Cube Garden W60 x D30 x H36 (cm); Lighting: Green Glow/604 (NA Lamp 20W x 4) turned on for 10 hours per day; Filtration: Super Jet Filter ES-600; Substrate: Aqua Soil Amazonia, Power Sand S; CO2: 1 bubble per second using Pollen Glass and CO2 Glass Counter; Water Changes: Small volume at a time; Aquatic Plants: Glossostigma elatinoides, Echinodorus tenellus; Cryptocoryne wendtii, Green Rotala, Rotala macrandra Narrow, Ludwigia, Hygrophila; Others: Caridina japonica, Otocinclus; Water quality: Measured with Pack Checkers and various Tropic Marine Test kits

Characteristics of media and their combinations

It is evident through the experiment that it is important to establish a biological filter as early as possible (from the start if possible) and stabilize the water condition to encourage aquatic plants to start growing quickly and to promote the water purification capability of aquatic plants quickly. When setting up an aquarium, water purification should be performed with a somewhat large amount of anthracite or NA Carbon. NA Carbon is a high capacity activated carbon with uniform size pellets that allow water to penetrate them well and provide uniform filtration. It has an adsorption capacity that is 20 times as effective as ordinary activated carbons. ADA offers another adsorption media called Bamboo Charcoal. Its raw material is highly porous bamboo charcoal which has a large surface area. This media is hard and does not crumble easily. After it loses its adsorption ability, it can be continuously used as biological filter media that filter bacteria colonize. The main media for biological filtration is Bio Rio. As stated earlier, Bio Rio contains dormant bacteria spores, which multiply fast upon introduction and establish biological filtration at an early stage. Bio Cube consists of polyurethane sponges. Bacteria colonize this type of plastic media surprisingly fast and biological filtration starts up smoothly. The sooner a biological filter starts functioning the better since it leads to a stable aquarium condition. Therefore Bio Rio or Bio Cube is used in combination with adsorption media. Once the water condition is stable, the ratio of activated carbon is reduced gradually to allow most of the filter media to function as a biological filter. Although any fine media can work as a mechanical filter, Palm Net has a unique characteristic that other media do not have. This media is made from the net-like fibers that cover the trunks of Windmill Palm in the family Arecaceae, which used to be used for filtering well water for drinking in the past. Since it has an ability to suppress germs, it has been used as spawning media for ornamental fish. It is wonderful to apply such an old wisdom to modern day aquariums.

Clogged filter media and its cleaning

Microbes colonize biological filter media forming a network (biofilm). Since a large surface area is required to colonize a large number of microbes, porous media with a large surface area is most efficient. Fine filter media are more efficient since large particles waste space in a filter because of the big space between the particles. However, porous and fine media tend to get clogged more easily. The capability of a biological filter reaches its peak when the filter is about to start clogging. As the filter starts to clog, the water flow decreases, the oxygen level inside filter media decreases as well, and the filtering capability drops rapidly. However, if a filter pump has a high capacity (pump head), it can maintain a high water flow through the media and therefore a high filtering capacity for a long time. The pump for Super Jet Filter was developed with this in mind. However, it also requires maintenance as the filter becomes clogged to some extent. When this happens, media should be taken out and rinsed lightly to wash off dirt using water from the aquarium and taking care not to scrub off too many microbes.

Relationship with water changes

An aquarium with a well functioning filter has high water clarity, healthy aquatic plants and fish, and very little algae. The frequency and the volume of water changes can be reasonably small as well. On the other hand, if filtering capacity is low, such as when the aquarium is just set up, it is necessary to increase the frequency and the volume of water changes to overcome difficulties. As this indicates, there is a relationship between filtration and water changes. Selecting and combining proper filter media leads to maintaining the beautiful aquascape of Nature Aquarium.