Types of Filtration

MECHANICAL

Mechanical Filter

This is the stage of the filter where water is pumped from the tank, through and out of the filter. This process is simply to eliminate any debris or larger particles floating in the water, thus reducing pollution. As debris is filtered through your mechanical filteration, the media inside will gradually build up with waste. It is important to keep this filter clean. It is crucial that you clean it only when the cleaning is absolutely necessary. Clean it gently with water that is taken directly from the tank and not tap water, ensuring that your biological filter is not damaged. I only clean my mechanical filtration media once every three months or so. However, how frequently you clean your filter will vary greatly according to the size and stock of your tank. As a rule of thumb, don’t clean your mechanical filtration media unless the waste is causing a blockage, or is at a stage where it can’t catch any more waste.

BIOLOGICAL

Biological Hang-On Filter

The biological filter or “biofilter” is the most complex, yet important stage of filtration. Fish naturally produce waste, and once this enters your aquarium it’s quickly converted into ammonia. The biofilter absorbs ammonia, thus producing both nitrifying and denitrifying bacteria, which will break down ammonia into less harmful chemicals. Once ammonia is present in a tank, nitrifying bacteria will start to cultivate, and will then begin to eat the ammonia and excrete nitrite, a slightly less toxic chemical. Once nitrite is present, denitrifying bacteria will start to cultivate, and will then begin to eat the nitrite and excrete an even less toxic chemical, nitrate. This is known as ‘the nitrogen cycle’ or ‘nitrification’. When an aquarium is first started, no biofilter is present and therefore there is nothing to break down toxic ammonia. The process of building your biofilter is called cycling, which we discus in another Learning Center article. If you introduce fragile fish into a tank that is not yet cycled, they will likely die from ammonia poisoning, which is also appropriately known as “new tank syndrome.”

CHEMICAL

The final stage of the filtration system is known as chemical filtration. This stage is not actually necessary; however, it is used by most serious aquarists in order to maintain premium water quality for their discus. You can think of the chemical filtration as a manmade version of the biological filter, as is used to remove chemicals from the water. However, this doesn’t mean that you can use chemical filtration as a substitute for biological filtration. Chemical filtration media includes products such as ‘Seachem Purigen’, ‘Seachem Matrix Carbon’ and other miscellaneous chemical eliminators. Chemical filtration media will all at some stage deplete, and some will actually return the toxins that they have absorbed, back into the water. Therefore, it is essential to monitor your the chemical filtration media and read the directions to get an idea of how long these products will last in your aquarium before depleting.

QUESTIONS

• Which types of filtration do you use in your discus aquarium?
• Why are these different types of filtration important for discus aquariums?
• Why are biological filters the most important source of filtration?