Four types of sponges with different cell sizes
One of the main tasks of an aquarist is to ensure adequate living conditions for their pets, in particular, the cleanliness of the aquarium and the optimal hydrochemical parameters. Installation of the filter solves a number of problems associated with the maintenance of the aquarium, and also contributes to the establishment of biological equilibrium in the reservoir. However, this is achieved only by proper selection of the filter and fillers to it. The preferred filter strength depends on the size of the tank, the number of fish and how often the aquarist wants to clean it.
Experts in the field of aquarium fish farming recommend using more than one operating filter per container, which is due to the possibility of contamination or the failure of one of them.
For effective water purification, a three-stage, mechanical, biological and chemical filtration must be carried out. Low-porous and highly porous sponges, polyester fibers that can trap organic and inorganic particles, are usually used as a filler for mechanical cleaning. As a rule, water enters the filtering material with a pump, or sublimates with air bubbles in airlift systems. Over time, the remnants of feed, excrement and other waste contaminate it, thereby complicating the flow of water and reducing filtration efficiency. Therefore, regular flushing or updating of the filler is required.
Sponge coarse mechanical cleaning on the left and one highly porous sponge on the right.
The operation of the filter is associated not only with the collection of particles, but also with the neutralization of chemicals formed in a closed biological system. Chemical cleaning prevents reactions between substances, accumulates toxins, chlorine, heavy metals and drugs that are dangerous for fish, plants and other organisms. This task is performed by a carbon filter, a charcoal filler, zeolites and ion exchange resins.
Activated carbon, due to its fine porous structure, is able to adsorb toxins, humic acids, vitamins and trace elements. Its use is justified after medical treatment of fish to remove residual medication, as well as immediately after the launch of the aquarium for dechlorination. Zeolites have the form of gravel and are minerals from the group of aqueous aluminum silicates of alkali and alkaline earth elements. The specific spatial structure makes them excellent adsorbents. Ion exchange resins are produced in special bags that are placed in a flow filter. Depending on the type, they are able to pick up certain ions from the water and, as a result of the substitution reaction, absorb them into themselves, giving up another ion.
The duration of operation of fillers for chemical filtration is limited. Aquarists who do not want to regularly replace activated carbon or zeolites risk poisoning their pets, because by adsorbing toxins and running out of resources, they will start releasing chemicals back into the water.
Probably the most important component in the context of the removal of toxic substances is biological filtration. A feature of this type of cleaning is the involvement of a number of beneficial bacteria. At the first stage, ammonia (released from the gills by fish), which is part of ammonium salts, is oxidized by nitrifying bacteria (Nitrosomonas) to nitrite (NO2) with the formation of salts of nitrous acid. At the second stage, nitrobacteria (Nitrobacter) oxidize nitrites, converting them to nitrates (NO3). The resulting salts of nitric acid are easily absorbed by higher aquatic plants, or, in their absence, can be removed from the aquarium by periodic water changes. The Nitrosomonas and Nitrobacter populations form a bacterial film on any substrate, including soil, plants, glass, decorations and filter media. However, the most effective removal of nitrite and ammonium occurs during the passage of water through porous material, sponges, special ceramic rings and plastic balls, which provide bacteria with a large area for growth. In addition, a special biological filtration filler is better aerated and, thereby, activates the aerobic nitrification processes. It should be noted that the development of a bacterial film inside a carbon filter is limited, probably due to the absence of oxygen and the presence of toxins.
The filler material for biological filtration in the process of work is contaminated with organic waste, therefore, it is necessary to periodically wash it. This procedure should be performed with distilled or aquarium water, as rinsing with chlorinated and hot water tap will cause the population of beneficial bacteria to die.
Biofilters for biological filtration (from left to right): Aqua Medic BactoBalls, SunSun Bio Ball HJS-328 and Teratec BB (ill. Aquaforum.lviv.ua/forum/showthread.php?t=5719). Ceramic rings for splitting water flow (left) and for biological filtration (right).
Very often, aquarists have a question about the correct location of the fillers in the filter. In this case, you need to be guided by the direction of water flow, where it flows into the filter, how it moves in it and from where it rushes into the aquarium. Ceramic rings should be placed at the entry point to split the water flow and distribute it evenly over the entire filter area. In particular, if in the external filter water flows from the bottom up, the rings fall asleep on the bottom of the canister, while they should be arranged randomly, and not in even rows. A large-pore sponge of rough mechanical cleaning is put behind the rings, then a small-pored sponge. After the sponges, a highly porous biosubstrate or biosharik is placed for the culture of nitrifying bacteria. At the entrance to the rotor, a synthetic winterizer is placed to protect the blades from large solid particles. If necessary, sorbents (coal, ion exchange resins) are placed after biosubstrate.
Most of the external and internal filters for the aquarium carry out biological treatment, during which the nitrogen cycle is terminated at the nitrate stage. The latter, in most cases, is removed by water changes, or absorbed by algae and higher plants. But sometimes nitrates are removed using special nitrate filters (nitrate reducing gears), sulfur filters, and also aquaponic systems. In the case of nitrate filters, an anaerobic environment is created in which the bacteria Pseudomonas denitrificans, Pseudomonas aeruginosa, Paracoccus denitrificans or Bacillus licheniformis transform NO.3 into gaseous nitrogen or nitrous oxide. Sulfur filters use a population of sulfur bacteria Thiomicrospira denitrificans and Thiobacillus clenitrificans, which oxidize sulfur and at the same time convert nitrate into nitrogen gas.
Adding a hydroponic module to the aquarium water recirculation system allows the removal of nitrate salts by their uptake by land plants.