Understanding the basics of planted tank maintenance is an absolute necessity in the aquarium hobby. The first step to understanding this is knowing that aquarium fish inhabiting the planted tank produce contamination. Ammonia, a very toxic substance, is produced by fish and other fauna through excrement and respiration. Aquatic plants create this through decomposing leaves. A milligram of this substance per liter of water would easily wipe out all the tank’s inhabitants. Nitrites, Nitrates, and other elements are also going to be present in the aquarium water as well which in the right amounts could equally be as lethal. Understanding the process of removing these harmful substances from the water should be the number one priority of any freshwater aquarium owner.

Adequate aquarium filtration will successfully remove these toxic compounds from the aquarium. It also lessens weekly maintenance chores by about 50% and ensures stable water parameters which greatly contributes to the health of the aquarium fish.

Aquarium water filtration can be divided into 3 basic phases. Phase 1 (mechanical filtration) is the removal of all that would possibly cause excess ammonia and other compounds from your aquarium. This includes fish waste, dead leaves of aquatic plants, and other decaying organic waste such as uneaten food. Phase 2 (biological filtration) is the conversion of ammonia, nitrate, and other compounds into less toxic substances that aquarium fish can hadle and Phase 3 (chemical filtration) is the actual removal of certain chemicals that might be present in the water of the fish tank. Having all 3 phases applied correctly in any aquarium filtration system would generate safe and crystal-clear water allowing your planted tank to show its natural beauty.

Mechanical filtration

     Any material that filters out debris or solid particles out of the water and does not leach any substances will do. Consider the flow rate of the pump as this will dictate how fast the mechanical filtration will work. This process is not only done in order to keep the aquarium looking clean, it is also there to protect the biological and chemical filters from being totally covered with decaying matter so put it first where the water flows in your filter. An efficient mechanical filter should remove at least 75 % of all the suspended solids before pushing the water into the second phase. This in the long run would mean less filter maintenance for it is only the mechanical filter that would require cleaning or replacing since it is the only one that is going to be ridden with gunk.

  This phase of filtration can be as simple as running the water into a layer or several layers of filter wool or as complicated as having multiple chambers dedicated for the purpose.

  The most commonly used is Filter wool/filter pad as this material has the capacity to strain out aquarium waste from the water effectively. They come in different kinds. Coarse filter pads with bigger pores are perfect for larger tanks with bigger fish as it has the capacity to handle larger amounts of waste without clogging. Finer pads with smaller pores are perfect for keeping your aquarium water clear as these will remove the tiny particles suspended in your water. A combination of both is commonly used. Eventually, all mechanical filter media will clog and will need to be cleaned or replaced.

Sponge filters work great as well as they function as both mechanical and biological filters. They are not the best mechanical filters out on the market but the pores in the sponge which make ideal homes for the beneficial bacteria will more than compensate for its low capacity to filter bigger waste particles. If used properly this type of filter is perfect for polishing aquarium water. 

Biological filtration

There are certain types of bacteria living in water that will eat ammonia and convert it to Nitrite. Another type of bacteria eats the still toxic Nitrite and converts it to the less toxic Nitrate. This is called the Nitrogen Cycle. This is what all aquarists rely on to keep their tanks healthy and happy. 

Simply put, this type of filter media houses beneficial bacteria. Tests have shown that nitrifying bacteria live on almost any surface. These bacteria are Aerobic types. It is important for them to have oxygen so they must be housed in a place in the fish tank where water will pass thoroughly. They will get oxygen from the passing water while ridding it of ammonia and nitrites. The Nitrogen Cycle happens everywhere in the freshwater aquariums but should mostly happen where all the water would pass through the filter. 

Ceramic rings are designed to take up less space but provide the maximum surface area for the bacteria to live on. They are also designed so water can flow freely through them. There are dozens of products out on the market. Just bear in mind that when selecting media, it should be porous and should allow the water to flow through. 

As known to experienced aquarists, it takes about 3 weeks or more for beneficial bacteria to be established and fully functioning in the freshwater planted aquarium. It is important for newly setup planted aquariums to have lesser inhabitants during this period since fluctuations of Ammonia and Nitrite are common. This is known as “cycling”. Introducing bacteria into a newly setup aquarium helps to speed up this process. There are products out on the market which are designed for this purpose. Some experienced aquarists though usually take a piece of filter media from an old fully established fish tank and put it in the new filter. 

Chemical filtration

There are only a few materials, two to be specific which are considered to be excellent at this. Where there is a lack of technology though nature once again is more than willing to help out. Live plants will readily absorb most of the chemicals found in the water column. This is where planted aquariums have an advantage over fish tanks containing only fish. 

Discussion for this phase will mainly focus on the most common substances found in your aquarium. Nitrate, the by-product of the “Nitrogen Cycle” is top on the list. Nitrate (Nitrogen) is one of the 3 macronutrients that aquarium plants need. Aqurium plants absorb what they can of this stuff. The key is to find the right number of plants to absorb what nitrates your aquarium products on a daily basis. It may turn out that maintaining the right levels of nitrates in your fish tank requires just a few plants.

The handful of products out there that are considered good, will, in fact, absorb almost anything from the water column. They don’t discriminate about which to absorb and therein lies the problem. Some chemicals you put in the aquarium such as fish medicine, water conditioners or plant fertilizer might wind up only getting absorbed by the filter system within a few hours. 

The most popular of these products is Activated carbon. Nothing beats this material in terms of its absorbing capacity and availability. Placing this on the last chamber of the aquarium filter would be highly recommended for newly set-up planted tank.

Synthetic absorbent resins are slowly gaining in popularity during the last few years. They do come in handy as they can be recharged meaning they can still be reused whereas activated carbon must be discarded after a few months of use.

Other products involve adding even more chemicals into the water to get rid of the unwanted ones. This is a bad idea. There are too many unknown variables to risk using these products. 

The regular water change

It is inevitable that with time there are certain elements that would build up in the aquarium water. To remedy this problem, regular water changes must be done. This will reset the aquarium parameters back to safe levels depending on how much is taken out and replaced. Safe amounts of water to be changed would be anywhere from 30% – 70%. Doing 100% water change would be risking the fish going into shock. Doing less than 30% does not do much to your tank. Learn to love the weekly water changes as this could mean the difference between success and failure. 

The cleaning up crew

Sometimes it turns out that aquarium filters installed in our fish tank is not sufficient. Then the aquarium cleaning-up crew is very welcome. It’s worth to put some algae eating fish or snails in order to control the algae growth better. There are some fish species that specialize in eating different kind of algae, e.g. young individuals Black Molly are interested in blue green algae the most. Look for other species in our BLOG describing best animals to control the algae growth.


To sum up, if you’re a beginner to planted tanks, understanding the filtration system is the key factor that affects the entire tank. We really hope that if you’re planning to set up your first planted aquarium, this article helped you to understand the filtration process in the aquarium.

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