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    Sludge in your aquarium

    Useful or not?

    Many inexperienced aquarists simply regard sludge as dirt and thus as a "harmful substance". That's not quite true though! Here we explain everything important to you about sludge.

    What is sludge?

    In an aquarium, sludge is a brown, rather flaky-airy stuff, collecting on the substrate after time. However, it can also be found inside the filter, but there it is referred to as filter sludge. Sludge basically consists of degrading biomass. This can be dead plant parts, but also leftovers and excrements of fish and invertebrates. This variety of organic material is processed and degraded by many microorganisms. From tiny snails, worms and unicellulars to mushrooms and bacteria, there is a lot of life in the muck! These different creatures are extremely important to the aquarium's ecosystem, as they shred organic waste and contribute to the degradation of pollutants. These organisms include, among others, the nitrifying bacteria, which are involved in the nitrogen cycle, in the course of which they oxidize ammonium to nitrite and nitrite to nitrate. For this very reason, "second-hand sludge” from an aquarium with an already longer service life - ie from an ecologically established aquarium - is gladly used to "inoculate" a new setup with microorganisms.

    Sludge and aquatic plants

    There are various connections between sludge and aquatic plants. The roots anchored in the substrate supply oxygen to the microorganisms living in the sludge which they need to break down their food. On the other hand, the humic complexes found in the sludge act as chelators: they bind minerals. If the sludge is decomposed further, the minerals become free again and will be available to the plants. Casually speaking, sludge serves as a buffer for nutrients.

    Roots of aquarium plants

    Extract sludge...or not?

    In fact, there are quite a few arguments that the sludge is important for the ecosystem in the aquarium and therefore should not be removed. In a well-balanced system (after the cycling phase) there is usually always the same amount of sludge present in the tank. If so, it does not need to be extracted regularly. On the contrary, this would disturb the aquarium’s microbiology and equate to a reboot of the ecosystem. If you want to extract mulch from the aquarium anyway, only a part of it should be removed for the reasons mentioned above.

    Plant roots

    When understanding sludge as a living part of the ecosystem, it is consequently important that the right living conditions are met. Above all, the bacteria in the sludge need oxygen for their metabolic processes. Therefore, as an aquarium owner, you should make sure that an adequate oxygen supply is guaranteed. This includes a sufficient stream and the presence of aquatic plants. Compacting the substrate should be prevented. Otherwise, dead zones may build in the soil, and there is a risk of digester gases forming. This is an indication of an eutrophication of the microbiology in the aquarium. Following this, the aerobic bacteria, which need oxygen, die in large quantities, and other bacteria will multiply, which produce sulfur gases due to their anaerobic lifestyle. This can get very dangerous for the aquarium’s inhabitants. In that case you need to remove all rot and the connected organic mass as soon and thorough as possible as well as the cause of the lack of oxygen.

    sludge in the substrate

    If too much sludge seeps into the soil, densification can be the result.

    Especially in systems with excessive stocking and according feeding, significantly more sludge can form over time, often accompanied by increasing levels of nitrate and phosphate in the water. If the water pollution is too high, it can no longer be adequately processed by the existing ecosystem. An imbalance will occur. The ever-growing mass of sludge can further compress the substrate more and more which will lead to the abovementioned dead zones in the tank and the formation of digester gases. By now, the aquarist should step in and support the ecosystem. Regular water changes help reduce the water pollution, and a resolute reduction of the sludge cover prevents the formation of rot spots in the ground. Furthermore, you should do research on causes, possibly change or reduce the feeding and improve the filter performance in the aquarium.

    Remove sludge

    There are several ways to remove sludge from the aquarium. First of all the sludge can be easily extracted with a hose. Practically, sludge usually accumulates in very specific places in the aquarium, namely, in low-flow zones. Most are located in the corners of the tank; The particles can settle there well. If neither filtering nor flow are changed, the position of the sludgecorners won’t change either.

    gravel cleaner

    In case ground-burrowing inhabitants have worked the sludge too deeply into the substrate, syphon cleaners help cleaning the substrate. Through the bell-shaped syphon only light particles are sucked in, while heavier grains sink back to the ground. In this way, the least possible amount of sand, gravel or soil is removed during the cleaning process.

    Another possibility would be the use of sludge reducing agents such as gravel and substrate cleaners. Most of these agents are bacterial preparations, which help break down already accrued organic material. Additionally the water quality will be improved and the water will clear up.