Even though a lot of aquarists believe that their aquarium is kept perfectly clean by the filter, this is nothing but a fairy tale. A filter to keep the aquarium floor, the spaces between the decorations and the water clean would have to produce a current strong enough to make the fish all (and very clearly visibly) stick to the glass pane! Jacuzzi aquariums are not everyone's cup of tea, so in 99% of all aquariums dirt is deposited in the substrate and between the decorative elements, and we need to help the filter by carrying out regular partial water changes with a substrate cleaner (such as JBL PROCLEAN AQUA EX 20-45 ). Using a gravel cleaner in connection with a 30% partial water change every 14 days is the most important maintenance step you can carry out in your aquarium!
The main task of your filter is to provide settlement space for your pollutant-degrading bacteria. While these beneficial bacteria also live in the substrate and on any decorative elements in your aquarium, the amount is very small compared to the bacteria population in the filter. About 90% of your helpful bacteria live in the external filter sized to fit your aquarium!
The filter structure
Let's take a closer look at what happens in your filter:
It all starts with the suction strainer, which is designed to prevent fish from unintentionally ending up in the filter. At the same time, it keeps coarse plant matter from clogging the inside of the filter. This works quite well, but of course it also reduces the water flow. So check your filter basket at least once a week and remove the coarse dirt.
Some of the coarse dirt gets into your filter with fine dirt particles, faeces and lots of aquarium water. Now we need to distinguish a little between internal and external filters. Modern internal filters are designed so that you can use different filter materials, but not one after the other, as in the external filter. This feature and the smaller filter volume are the main disadvantages of all internal filters. Therefore, let's return to the external filter:
The filter material
Ideally, your external filter has pre-filter material that is coarse foam with 15 to 35 ppi ( p ores p er i nch (2.5 cm)). Coarse dirt, which would otherwise clog the subsequent filter material too quickly, is caught here. This is also the reason why the filter material should always be staggered from coarse to fine. Some bacteria to break down the accumulating coarse organic matter will settle on the coarse foam, but unfortunately not all that many. The main function of the pre-filter is more of a mechanical nature. After the pre-filter, most filters use ceramic tubes that work partly mechanically and partly biologically. They are coarse enough not to clog too quickly and at the same time have a certain surface area so that bacteria settling there can break down pollutants. The organic matter from faeces and plant residues, for example, consists of proteins that are converted to ammonium (NH4) by a certain group of bacteria (heterotrophs). Ammonium itself is not toxic to fish and invertebrates. Nevertheless, high ammonium levels can lead to growth inhibition. In addition, part of the ammonium becomes toxic ammonia (NH3) at pH values above 6.8. Thus, a problem-free ammonium content of 0.8 mg/l at pH 7.3-8.3 can already lead to 0.028-0.082 mg/l ammonia. These ammonia levels lead to serious organ damage in fish in the long run. If the pH rises to 8.4, e.g. due to a partial water change with tap water, even more ammonium becomes toxic ammonia and the value rises to a lethal 0.1 mg/l. An immediate remedy in this case would be to lower the pH value by pH-Minus or addition of CO2.
In the filter, however, the bacteria convert substances at the same time, and the ammonium produced is immediately processed further. Unfortunately, the subsequent product is no better, because it is toxic nitrite (NO2). Since nitrite looks like oxygen on a molecular level, it blocks the transport of oxygen in the blood of living organisms (including humans) and leads to internal asphyxiation. In the aquarium, you should always aim for nitrite to have the lowest measurable value ( 0.01 mg/l) using commercially available water tests. In plain language: there shouldn’t be any! Any presence of nitrite tells you unmistakably that your bacteria are either missing, are insufficient, or are not doing their job. Bacteria starters (such as JBL Denitrol ), partial water changes and a check of the food amount or fish stock are possible countermeasures. In any case, you need to act urgently. The only exception: Your aquarium is new and it is in the run-in phase. Then a temporary nitrite peak is part of the normal run-in process.
But now you don't have to worry that your filter will permanently release toxic nitrite into your aquarium water, because the same bacteria not only process ammonium into nitrite, but also nitrite into non-toxic nitrate (NO3). Even if you've pushed chemistry to the back of your mind as an unpleasant memory from your school days, it's worth taking a look at the chemical formulas to understand what's going on. Once the proteins have been converted to ammonium/ammonia, it's all about the oxygen. As long as oxygen is present, and basically oxygen is not in short supply in your filter, the bacteria will build up more and more oxygen to the nitrogen atom. NH4 becomes NO2 (2 oxygen atoms) and then NO3 (3 oxygen atoms). You may not really care, but the important thing to remember is that enormous amounts of oxygen are consumed in these biological degradation processes. The heavier your water load from fish, food and plant debris, the more oxygen your aquarium (and thus your bacteria) needs. Be sure to ensure that the water output from your filter results in a LIGHT water surface movement. This will allow your aquarium water to absorb enough oxygen and not expel too much CO2 (carbon dioxide). Your plants will appreciate this, as CO2 is their main nutrient!
Normally, EVERY filter, whether internal or external, will produce nitrate. Nitrate is non-toxic, but unfortunately serves as food for algae (and plants). If a nitrate test shows more than 30 mg/l nitrate, you need to take countermeasures. There are good nitrate-reducing filter materials that break down nitrate biologically.
Your filter is certainly the most important technical aid for your aquarium. But please keep in mind that you absolutely have to help with regular partial water changes involving substrate cleans. And please clean your filter regularly – especially the pre-filters - every 4-8 weeks! And don't forget: Remedies, salt additions and intensive cleaning can adversely affect or even completely kill your filter bacteria. Then there is no alternative to a restart with a good bacteria starter!
The microscope images substantiate the finding that filters can indeed become "breeding chambers" for pathogenic (disease-causing) bacteria. In addition to the pollutant-degrading bacteria, spirillum types can also be seen in the image. These are among the pathogenic germs. Therefore, filters need to be cleaned regularly and re-inoculated with a good bacterial starter. In this way, recolonization can take place very quickly and pathogenic germs are not given enough time to multiply.