As the name implies filter “under gravel” is a filter which is located below a layer of “gravel” (gravel, sand) at the bottom of the aquarium. Its construction consists of a layer of anti-rust material (plastic) perforated with bearing feet so as to create free space underneath to allow water to flow (Figure 5). In one of its corners (or more) are piping the output to return the water into the aquarium filtration results.
Figure 5. Example of Construction Filter “Under Gravel”.
Figure 6. Mechanism A Filter “Under Gravel”
Figure 6 shows the mechanism of action of a filter “under gravel”. In this case the water was “forced” to break through layers of gravel at the bottom of the aquarium with the help of head pump or aerator, then the water is returned into the aquarium. At the time of water through water gravel undergo at least two filtration processes, namely mechanical, through the pores effectively gravel layer, and biology, through the contact of water with ammonia and nitrite-degrading bacteria that live on the surface of the gravel.
Biological filtration systems play a major role in this filter. Over time, the buildup of solid particles in the space between the gravel can cause a blockage. Therefore, under gravel filter is recommended for in-patient periodically, at least by estab-vacuum-an on gravel. Blockage can lead to a condition anaeraobik on gravel environment that can lead to bacterial decomposition of ammonia and nitrite die which may eventually result filter malfunction.
Under gravel filters are often used especially in the marine aquarium. In this filter system, organic particles are trapped on the surface of the gravel will be a source of food for microorganisms (plankton). Furthermore plantkon be a source of food for other marine inhabitants are maintained, particularly from the class of plankton. Thus, the filter “under gravel” in the marine aquarium as if it serves also as a refugium.
Under Gravel Filter Reverse (Reverse Flow Under Gravel Filter)
One of the problems in using under gravel filter is likely to be blockage of the flow as a result of the accumulation of dirt that can not be processed quickly. This debris can accumulate between the gravel, causing blockage which in turn can reduce the performance of the filter. One solution is to relatively frequent menyipon and clean the gravel layer on a regular basis. The cleaning should be done partially, so that bacterial decomposition is not exhausted “washed away”.
Another way is to separate the sediment from the gravel. This can be done using methods fiter under gravel with the flow reversed. Figure 7 shows a diagram of how the separation is made. The separation of the deposition process is done by adding a filter unit outside the main aquarium. The main task of this filter is to perform mechanical filtration (A canister filter may be used to perform this task).
After a mechanical filtration process, the water is then returned (with the aid of a pump) into the main aquarium via pipes let out under gravel filter. Furthermore, the water will spread out below under gravel filter and then through the layer of gravel. At the time through the gravel layer is water undergoes biological filtration process. Thus when water is back in the main room of the aquarium is expected to have been freed from ammonia.
Figure 7. Filter under gravel with water flow reversed.