Filter Material for the Pond: You Have to Know That

It all depends on the right filter material: Filters are their own small power plants and keep the pond and its ecosystem running. In this article, you can find out what you should pay attention to when cleaning and maintaining your filter in order to ensure a functioning pond and healthy pond water.

General information on the filter material

Each filter consists of different filter materials – also known as filter media. The derivation comes from the fact that the corresponding sponges, stones, tubes, balls, fleeces or adsorbers represent surfaces on which countless cleansing bacteria live. The bacteria settle everywhere: they live on the pond liner, on the plant basket, even in the hose of the filter pump. There they feed on fish excrement and organic residues.

The durability of a filter

A single filter sponge – in A4 format with a thickness of 5 cm – has a larger surface area than all other (pond) areas combined. This is due to the fact that the sponges are foamed and work like a very dense network system that is “ventilated” through tiny air channels and hollow chambers. The material itself is usually made of plastic, which over time loses its plasticizer and can become porous. This process is accelerated by UVC water clarifiers, which enrich the water with ozone, which has an irritating effect on soft materials (sponges). The UV light from the sun also has a damaging effect on filter materials.

Accordingly, a commercially available filter sponge has a “reasonable” useful life of around six months. Then the structure of the plastic slowly disintegrates. When you can break individual pieces of fiber out of the sponge with your fingers, it’s time to replace the filter material. Please note that you should never change the entire filter material at the same time, otherwise the microfauna necessary to break down the toxins that occur is missing.

Another reason for regularly replacing the mechanically filtering materials such as fleece, sponges, and mats is the fact that residues of metabolic processes accumulate deep inside the material. You cannot remove these deposits, even if you clean the filter material under running water or wring it out several times in a bucket of water. As a result, the sponge condenses more and more until the water-resistance increases and the flow rate of the water visibly decreases. The time until the next blockage after cleaning is getting shorter and shorter. In addition, the frequent interventions in the filter disrupt the biological stability of the water. Since ponds have a particularly heavy load of dirt particles, this factor is a very important one. Last but not least, mechanical cleaning is the basis for further (biological) filtering. A filter that clogs quickly is overwhelmed and should be checked with regard to the filter material.

Spoiled for choice

When choosing the biological filter media, some things can also be done wrong:
Unfortunately, there are still pond fans who use simple gravel and ignore that the material surface of ten liters of gravel is roughly the same as that of one liter of the special filter substrate. This means that 90 percent of the possible filter performance is not used efficiently. Inferior lava split from hardware stores is also unsuitable because it is very dense and, like gravel, has a comparatively small surface structure. Furthermore, it is possible that lava split, which is actually intended for sidewalk areas, contains heavy metal inclusions. These are known to be highly toxic for the entire pond system and can spontaneously eliminate the stock even years later.

Therefore, when buying filter substrate, make sure that you choose a product that is explicitly suitable for use in pond filter systems. However, you should also partially replace this material after about four to eight months, as the important pores become clogged and inefficient. Here, too, cleaning with water is only partially successful, as the microbiological slime layers gain substance and harden over time.

Adsorptive filter material oil

The importance of adsorptive filter media such as activated carbon and zeolite is far underestimated. Invisible environmental toxins from the atmosphere get into the pond water every day, which disrupts biological processes. Even microorganisms and invertebrates (snails, mussels) are sensitive to these stresses. Rainwater washes countless soot particles from the ambient air and flushes them into the pond. For example, kerosene was found in the water in pond areas near aircraft routes. Substances from birth control pills are also regularly present in tap water and subsequently in pond water. Bee pollen brings tons of algae nutrients into the pond environment.

You cannot initially perceive these negative effects with the naked eye. However, it can be that animals become sick out of nowhere or that the water loses its clarity. Activated filter carbon and mineral rocks such as zeolite belong to the group of ion exchangers and have the ability to attract and bind the environmental toxins mentioned like a magnet. The useful life of this filter media is difficult to measure. As a rule of thumb, you should renew this at least every eight weeks to prevent the substances from dissolving back into the water.

Re-dosing and ventilation

The most important point is the regular replenishment of fresh strains of the cleansing bacteria. Over time, every pond loses its self-cleaning power and slows down all degradation processes. In spring, in particular, you should add new inoculation cultures around weekly – around monthly over the course of the year.

Strong pond aeration 24/7 and the use of active oxygen in powder form are real boosters for all good bacteria. The reproduction rate of the tiny helpers increases rapidly, which gives the filter effect a real boost. In this way, the filter can process dirt even faster and more thoroughly. The use of these preparations is highly recommended for pond filter systems that have been running for many years. The preparations are completely harmless to the pond inhabitants. On the contrary, they too receive new vitality because they can breathe deeply in a relaxed manner. As a result, the pond inhabitants no longer have to put their energy into exhausting breathing, but can invest the proteins and fats obtained from the fish food in growth and the immune system.

Care pays off

It is definitely worthwhile for every pond enthusiast to observe these basics and to take care when selecting the filter media. If you follow the tips, you can enjoy a clean and functional pond, which your animals will certainly enjoy.

Mary Allen

Written by Mary Allen

Hello, I'm Mary! I've cared for many pet species including dogs, cats, guinea pigs, fish, and bearded dragons. I also have ten pets of my own currently. I've written many topics in this space including how-tos, informational articles, care guides, breed guides, and more.

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