Hey! Here’s a picture of an Eheim Classic 2217. I want to explain what filtration actually is and what is supposed to do.
There are three types of filtration: mechanical, biological, and chemical. In the picture above we can see the first two types of filtration.
Before I get into the three types, there is another type of media inside the canister. The dispersion substrat at the bottom of the Eheim Classic 2217 acts as small tunnels for water to go through and that allows for the intake of water to disperse evenly throughout the entire filter.
Mechanical filtration is the second layer from the bottom. It is a sponge that filters out debris from the aquarium such as fish waste, dead plants, anything that you do not want clogging the motor of the filter.
Biological filtration is the top layer in the picture above. This type of filtration is the most important and least understood aspect of a successful aquarium. This layer in the filter holds the majority of the beneficial bacteria colony that is inside of any aquarium. Why is bacteria important for an aquarium? The bacteria is a special type of nitrifying bacteria that is responsible for the nitrogen cycle. Here’s a visual.
The bacteria is the “Decomposers” part of the picture. When a new tank is being established, high levels of ammonia are present in the tank. Ammonia can come from a variety of things: fish waste, fish food, and even the soil substrate that is used in some planted aquariums. Ammonia is very dangerous to not only fish but also plants. Damage to tissues, gills, and kidneys are only some of the effects to livestock with the presence of ammonia. Some plants can tolerate some level of ammonia, but more delicate species tend to melt away.
Eventually, with the development of nitrifying bacteria, ammonia is converted into nitrite. This however, is also dangerous and damaging to livestock. For an aquarium to be safe for plants and fish, only nitrates can be present. Even then, only low levels of nitrates keep livestock healthy and happy. Plants help absorb nitrates and keep the aquarium balanced. (We’ll get further into the benefits of plants in a later post.)
The conversion from ammonia to nitrate can take weeks and even months. But with proper biological media and filtration, the conversion time can be reduced greatly. Below is a picture of standard biological media that is placed into a filter. These tiny balls are half the size of marbles and are extremely porous. Bacteria thrive and multiply within these pores, which is why this type of media is so effective.
The more biological media that a filter holds, the more stable it is. Once a good colony of nitrifying bacteria is cultured, ammonia and nitrites are usually never present, no matter what happens.
For example, if you accidentally overfeed and the uneaten food decomposes and becomes ammonia. This can spike ammonia levels and harm the livestock and plants. However, with an established bacteria colony, the ammonia will quickly become harmless nitrate. There will be no fluctuations in ammonia or nitrite levels with a large colony of nitrifying bacteria.
This is the reason why we prefer to use larger canister filters that hold large amounts of porous biological media over smaller filters. Bacteria can also grow in the sponges in filters, but not as much as biological media.
The third type of filtration is chemical filtration. This can’t be seen in the canister filter but it can be added in there. Media such as Purigen or Carbon filtration is a type of chemical filtration. This is not mandatory in an aquarium but it does help. It polishes the water in the aquarium and makes it look extra clean by removing any organic materials.
Filtration also provides water movement within an aquarium. This is important for many reasons. A good amount of flow allows for oxygen to be diffused into the water. If you are injecting carbon dioxide into an aquarium, you definitely want to have a strong filter to not only diffuse the CO2, but also enough flow to cause water agitation to keep the water oxygenated enough for the livestock. Lack of flow can also cause various types of algae.
Every single one of our aquariums are equipped with some model of Eheim. Each Eheim external canister filter excels in holding adequate amounts of biological and mechanical filtration. On top of that, a bag of purigen is also placed into the canister filters. This allows foor us to hold two to three times more livestock in our aquariums than normal. No matter how much ammonia is produced by the fish, our systems are stable enough to hold the livestock .
More informational blog posts to come! Cheers!