▷ Mulm in the aquarium | What is mulm and when does mulm need to be removed

What is mulm?

Sludge sucker in the aquarium | stock-adobe.com – madhourse – 244067475

Mulm mainly consists of the persistent residues of waste materials that accumulate in the aquarium. Typical waste materials in the aquarium are fish droppings, uneaten food and dead leaves.

Not all waste materials, e.g. B. fish excrement, directly on the ground and form the Mulm, but they are initially dissolved relatively quickly in the water.

These organic substances dissolved in the water are now broken down by bacteria in the filter and in the aquarium. Only the remnants of these degradation processes, which in turn are only broken down with difficulty, e.g. B. the humic substances, accumulate as visible sludge.

So Mulm is a mixture of waste materials and the remains of the biological degradation processes in the aquarium. Occasionally mulm is also referred to as detritus.

How and with what you remove mulm can be found in the article mulm vacuum cleaner.

If you don’t want to wait long, we have a pre-selection of mulch vacuum cleaners:

Mulm stabilizes the aquarium climate.

In the mulm, excellently useful bacteria can settle, which carry out degradation processes in the aquarium. At the same time, Mulm supports the flocculation of organic substances that are dissolved in the water. Furthermore, mulm offers an absorption surface, e.g. B. for iron ions on the humic substances, and supports the exchange of humic substances. As a result, substances that are in excess are stored in the sludge. Just as mulm absorbs substances that are in abundance, mulm also releases these substances when there is a shortage of these substances. Through these various effects, Mulm stabilizes the aquarium climate overall.

A certain amount of sludge in the aquarium makes sense and supports a stable running aquarium. The sludge continues to decompose, so that at the end of the so-called mineralization, hardly any noticeable amounts of end products remain. In an aquarium that is not too heavily stocked, a certain amount of sludge forms over time, which remains constant due to new additions and degradation (mineralization).

In addition to bacteria, other microorganisms also settle in the sludge, which are favorable for the aquarium climate and at the same time serve as food for fish and shrimp, especially the offspring.

Mulm should not be equated with dirt under any circumstances. It is often concluded that more mulm means more pollutants, e.g. B. feces, and thus ultimately causes increasing nitrite and nitrate levels. In fact, however, the sludge forms part of the nitrogen cycle in the aquarium. The bacteria settled in the sludge convert nitrite into nitrate, just like the bacteria in the filter. The amount of nitrate formed is therefore dependent on the amount of nitrite. The amount of nitrite depends on various factors such as stocking amount, amount of feed, etc.

Too much mud can also be harmful

Heavily agitated sludge in large quantities can e.g. B. lead to increased oxygen consumption in the aquarium and, in extreme cases, cause a lack of oxygen in small aquariums. The substance-binding property of the sludge can mean that plants receive too little nutrition if too much fertilizer is absorbed by the sludge. On the other hand, sludge itself is a good fertilizer and in times of shortage it can release fertilizers that were previously absorbed.

The bacteria that settle in the sludge break down pollutants like in the filter. To do this, they need oxygen, which has to be brought in again and again by a slight flow of water through the sludge. If oxygen becomes scarce due to a water flow failure or an increase in temperature, this can lead to the death of the bacteria. Like a filter with dead bacteria, the sludge can rot under such conditions and become extremely smelly. This can lead to a high level of pollution of the entire aquarium with dead organic residues.

How much mulm does the aquarium need?

If there is a large stock or too much feeding, more and more sludge can accumulate, which has to be vacuumed up every now and then. It should not be sucked off too thoroughly, but only about a third of the total amount, so as not to impair the stabilizing effect too much.

Increased accumulation of sludge can also be an indication that the filter is flowing through too quickly. The degrading bacteria are then flushed out of the filter in large quantities or do not have enough time to break down the pollutants in the filter because the contaminated water flows past too quickly. As a result, bacteria in the aquarium and on the substrate perform the main part of the degradation process, instead of bacteria in the filter. In such cases, the filter capacity is reduced until there is only a small water flow.

The effect is similar if the filter is too small and the degradation capacity of the filter is therefore too low. In this case, too, a large amount of the pollutants in the aquarium are broken down and settle as sludge. This explains why crystal clear water with hardly any sludge can be found in aquariums with large-area filters that have a high level of biodegradation capacity, while a lot of sludge often forms in aquariums with normal filters with fast water flow and correspondingly low biological decomposition capacity.

Unfortunately, it is not possible to predict which amount of sludge is useful for a specific aquarium and from which amount sludge becomes harmful and should therefore be vacuumed off. Here you have to approach the appropriate amount slowly and carefully. In any case, a balance should be sought in which the amount of debris remains constant and does not keep increasing. In this state, about as many pollutants are broken down as are newly formed. If more and more sludge forms, this is an indication that the biological decomposition processes in the aquarium are not sufficiently breaking down pollutants.

optics

It is a matter of taste whether one considers the sight of mulm in the aquarium to be natural or ugly. If the substrate falls slightly in the direction of the filter, most of the mulm collects near the filter.

On sandy soil, slight indentations form around the plants, in which the mulm settles and is partially covered. In the gravel bottom Mulm sinks into the ground. However, there is a risk that too much mulch will accumulate unnoticed and start to rot in the ground. In a well-running aquarium, however, only a small and constant amount of sludge accumulates in the gravel.

remove sludge

If the soil is sandy, the sludge collects on the surface of the soil and can be easily vacuumed from there. Over time you realize the distance…