In the aquarium, understanding the filtration mechanism is very important when we start, if not the most important. The aquarium is a closed system, hence the importance of filtering your water so that your fish do not swim perpetually in their own droppings. The filter is responsible for purifying the water in our aquarium by retaining waste and transforming certain waste through a biological cycle. We call this cycle the nitrogen cycle . Without filtration and therefore without a filter, aquarium water very quickly becomes deadly for our fish, with an accumulation of ammonia and nitrites, among others.

When we start, we are quickly lost because there are a lot of different filters and different budgets. Most of the time, when you buy an aquarium in stores, it is already equipped with a filter. But sometimes, this filter is not enough depending on the population of fish you have or want to put in it. There are therefore several types of filters that will be adapted to each need.

The two types of filters

There are two main types of filters: filters with a water pump and exhaust filters that work with an air pump.

For example, the internal filter will be fine for a population of small fish. The settling filter will also be suitable for the majority of community aquariums with an average fish population. On the other hand, as soon as we have big fish like goldfish, big cichlids, it becomes necessary to have an external filter which will be much more powerful to filter the mass of waste from the big fish.

The exhaust filter is generally used in breeding tanks so that the fry are not sucked in by the water pump. They are also highly recommended for aquariums with shrimp.

Filter feature

An aquarium filter is a modular technical element since you can change the filtration masks at your convenience and therefore adapt according to your needs, regardless of the type of filter you use. There are three types of filter media:

• mechanical filtration,
• chemical filtration and finally the most important,
• biological filtration.

Mechanical filtration

These are small blue foams and we say mechanical because they will retain the waste mechanically, they will prevent them from passing and simply retain them.

Chemical filtration

It is not about using chemicals to filter your aquarium but rather about using natural elements like activated carbon or peat to alter your water chemistry. For example, activated carbon will absorb the smell and color of your aquarium water. There will therefore be a chemical modification of it. Peat, on the other hand, will help to lower the pH, again by chemical action, but with natural elements.

Biological filtration

This type of filtration allows the good bacteria in your aquarium (those that are useful for the nitrogen cycle), to latch onto it and live there. It is therefore a very very important filtration. This type of filtration should be the majority in your filter.

When we start, we very often hesitate on the placement of the filter media . In what order should they be put? The main thing is to have plenty of biological filtration media, foam and ceramics.

How to choose my filter?

Choosing a filter is not easy, especially when you are a beginner. You must take into account several parameters and obviously also take into account your budget. The more powerful the filter, the bigger it will be and the more expensive it will be.

The first thing to see will therefore be the volume of your aquarium. Obviously a small 20 liter aquarium like will not have the same filtration needs as a 100 liter aquarium. The most important criterion for choosing your filter is your fish population . You need to see if you have big fish that pollute a lot, like goldfish, or small fish that won't pollute a lot.

Normally you will find an indication of flow rate / liters per hour on the packaging of the filters. This simply corresponds to the amount of water that the filter can filter in 1 hour. If you have a tropical community tank that is not overcrowded and there is a population of small fish, a filter capable of filtering your tank volume three times per hour is sufficient.

On the other hand, if you have an aquarium with large fish like goldfish, you will need a filter capable of filtering the volume of your aquarium five times per hour.

It should be noted that the settling filters and the internal filters are not very beautiful, moreover, they take up living space for your fish, which is rather a shame. Internal and settling filters tend to vibrate while external filters generally make no noticeable noise.

Finally, be aware that your filter must be on 24 hours a day and must never be turned off at the risk of killing all the good bacteria that have taken a long time to arrive in your filter.