Biofiltration in an aquarium is the process of converting ammonia (most harmful to all living inhabitants of the aquarium) into nitrites, and then into nitrates. The prefix "bio" means that this filtration process occurs with the participation of living organisms, i.e. beneficial bacteria that are in varying degrees, are in each aquarium.
Biofiltration is absolutely necessary for any aquarium, particles of dirt, waste products of fish, poor food or other organic matter tend to decompose in water, releasing large amounts of ammonia, which is extremely harmful to fish. If the aquarium has an insufficient amount of beneficial bacteria and poorly established biofiltration, the fish may get sick from ammonia poisoning, or die at all, as well as an outbreak of organic matter may result in algae outbreaks.
For good reproduction of bacteria responsible for biofiltration in an aquarium, only 2 conditions are necessary:
- The place where these bacteria settle large colonies;
- Constant flow of oxygen to the place of settlement of bacteria.
Bacteria for normal growth and nutrition must be attached to any surface, because in free swimming in water they will not be able to eat. The meaning of the biofilter is that the polluted water itself passes through the colonies of bacteria. Bacteria live on all surfaces of the aquarium, but since each bacterium occupies a certain (very small) area, for the reproduction of a large number of bacteria the area must be very large. Therefore, in the soil and filter them more than on the walls of the aquarium and decorations.
The process of converting ammonia into nitrates is associated with the absorption of oxygen, therefore, for the development of bacterial colonies, a constant supply of oxygen-rich water is necessary. From here, you can immediately conclude that in any part of your aquarium there is a poor circulation of water – there is not and cannot be this type of bacteria, even despite a large surface area, for example, the lower layers of soil.
Bacteria promoting biofiltration settle on mechanical filter sponges on various filter elements, since in filters there is a constant circulation of water enriched with oxygen. External canister filters are most adapted for biofiltration, due to the fact that the filler area is very high.
In principle, any specialized Fish Tank Filter that has a relatively high area of internal filler (or its volume) will be suitable for this purpose. For example, the bottom filter will use the aquarium soil as a place of colonization by bacteria. Porous ceramics are ideal for colonization by bacteria in a filter tank, since they have a very large surface area.
If you do not have money for an expensive filter, then you can purchase inexpensive attachments and accessories for filters or compressors that improve biofiltration in an aquarium, for example a bio-wheel or trickle, wet-dry filters.
The most important thing for bacteria is to provide a constant supply of fresh, oxygen-enriched water. If it stops, then in an hour or two the bacteria will start to die out gradually. Also, when choosing a filter element in the filters or the soil in the aquarium should not be taken too small. Instead of a very high surface area in this case, you get the difficulty enrichment of the entire volume of oxygen. For the same reason, it is necessary to periodically wash the filters, since The dirt accumulated in them complicates the access of fresh water to the colonies of bacteria.
A very good alternative to a biofilter is a dense population of an aquarium with plants with powerful lighting and CO2 supply. Plants absorb ammonia from water and nitrites are not worse than biofilters.
Now you understand the importance of such a process in your tank as the conversion of ammonia to nitrates. If at the moment you don’t have enough material means to buy a good biofilter, then I suggest you do your own home biofilter for the aquarium.
There is a huge variety of designs of such filters, they differ in performance, complexity and imagination of the authors. I will consider here several designs in order of the complexity of their manufacture, starting with the simplest. Having understood the basic principles, you can easily repeat any of them or come up with your own hand-made biofilter design.
one). When making a biofilter with your own hands, you will need a half-liter soda bottle, a plastic tube with a diameter equal to the inside diameter of the bottle neck, some small pebbles with a 2-5mm fraction, a synthetic winterizer, a compressor with a hose.
Plastic bottle is cut into 2 unequal parts: a large bottom and a small bowl with a neck. The bowl must tightly enter the deep bottom. In the bowl along the outer circumference we make several holes through which the water should freely enter. We make 2 rows of 4-6 holes with a diameter of 3-4 mm. We insert a plastic tube into the neck of the bowl, it is necessary that it comes under pressure and there is no gap between the neck and the tube, here you can show imagination. The tube should be flush with the bottom of the bowl. After installing the tube, we install the bowl into the other half of the bottle, while the tube length must be such that it goes out over the whole structure a little, and it does not have to rest against the bottom of the bottle so that water can freely enter it.
On top of the bowl we fall asleep 6-7 cm of gravel, and from above we cover it with a small layer of padding polyester. Inside the tube set the hose from the aerator (compressor) and fix it. After placing the whole structure in the aquarium and turning on the compressor, our filter will start working, and when it contains useful bacteria, it will be good for decomposing ammonia into nitrates.
The principle of operation: the whole structure is based on airlift, air bubbles from the compressor are fed into a plastic tube and immediately go up from it, while drawing down the water flows from the filter. At the same time, fresh oxygen-enriched water enters the upper part of the cup, passing through the entire layer of gravel, then passes through the holes made by us in the bowl and enters the lower part of the tube, from where it again tends to the aquarium. The synthetic winterizer in this design plays the role of a mechanical filter, which is needed to prevent rapid siltation of gravel in our biofilter.
2). The following design of the biofilter, which you can easily repeat at home with your own hands, is also based on the work of the airlift, so you will also need a compressor.
The design is very similar to the previous one; we take a plastic bottle of 1-1.5 liters (capacity depends on the power of your compressor and the volume of the aquarium). At the bottom of the bottle in a circle with an awl, we make a large number of holes (such a number so that water flows freely into the bottle). Holes must be made as low as possible so that the lower layers of gravel are also saturated with oxygen. Then the bottle is half filled with gravel (you can also use any biofiltration filler that will be used in filters, except very shallow ones, since water should easily circulate through the entire layer of filler), put sprayer connected to the compressor on top of the filler.
The principle of operation of this filter is as follows: under the action of the airlift, water is drawn out along with the air from the bottle, while again through the bottom openings in the bottle it enters it, saturating the entire layer of soil with oxygen. So that the filler in the bottle is less silted up – wind it in the place where the holes are made with thin foam rubber and secure with plastic clips.
By the two constructions described above, it can be understood that any biofilter consists of 2 parts: mechanical and biofiltration. After the mechanical filter, the water must pass through a biofiltration filler, this is where all the wisdom ends.
3). If an internal mechanical filter is already present in your aquarium, you can connect the output from it with any hermetic container filled with biofiltration filler or just fine gravel. On the one hand, the tank should receive clean and fresh water from the filter, on the other hand, the water should come out, a rather high-performance biofilter made with own hands is obtained. Since the flow of water from the pump is much more powerful than from the airlift – a container with a filler can be made of quite a large volume.
four). For very large aquariums, you can make a biofilter with your own hands using mechanical filter-flasks to clean tap water, as a pump you can adapt pumps for heating systems in private homes. Filters of the flask are connected 2 together, in one they leave mechanical filtration, and in the other they fill up the filler for biofiltration. After everything is tightly connected using fittings and water hoses. As a result, you will have a very high-performance external canister-type biofilter made with your own hands for ridiculous money.
I wish you good luck in your experiments and pure water in aquariums.