Filtration in a planted aquarium

When we talk about a planted aquarium, light, fertilizers, and CO2 supply often come to the fore. However, high-quality filtration is the invisible foundation without which this complex mechanism simply will not work stably. Its task is much broader than just making the water clear.

In an aquarium with a large number of plants, the filter performs several key roles. First, it creates a current that evenly distributes nutrients and carbon dioxide throughout the volume, preventing them from stagnating. Second, it is home to colonies of beneficial bacteria that process harmful fish waste products, converting ammonia into less toxic nitrates. These nitrates, in turn, serve as food for plants.

But there is an important nuance here: unlike an aquarium without plants, where the filter is the main fighter against pollution, in a planted aquarium, the plants themselves become powerful natural filters. Therefore, the aquarist's task is not to create a hurricane in the water, but to create a gentle but comprehensive current that will work in tandem with the flora, not against it. Choosing the right filter and setting it up correctly means finding a balance between cleanliness, circulation, and comfort for the inhabitants.

Main characteristics of filters

Pump power

this is the volume of water pumped through the filler per unit of time, measured in liters per hour. This refers specifically to the pump's power without taking into account the resistance of the filler. This is an important detail, as even clean filler reduces the pump's performance.

Over time, the filler becomes clogged and performance may drop to a minimum. This brings us to the first indicator of filter quality: the time it takes for the filter's performance to decline.

According to my observations, ADA, Eheim, and Aquael are the best in this regard. Many people are outraged by the extremely high prices of ADA products, but, for example, their external filter does not need to be washed for years, and this will not affect its performance or the condition of the aquarium.

The power of the external filter pump is selected based on conditions of ~ 100 l/h per 10 liters of water. This means that a 60-liter aquarium requires a filter with a pump capacity of ~ 600 l/h.

Remember this simple rule: if the flow from the filter outlet pipe has decreased, it is time to wash the filter media. Under no circumstances should it drop to zero. Do not allow a significant decrease in the water flow from the filter.

If the population of your aquarium does not change often, simply note the time it takes for the filter to become so dirty that it needs to be cleaned (a drop in power to 30%, but no more), and service the filter at regular intervals. I think this is the best solution.

Ability to adjust flow power

Some filters have this option (Aquael fan — 3, Eheim professional 5e, AQUAEL Ultramax 1000) — to reduce excessive flow from the filter.

This is usually done by moving the gate valve inside the filter structure, which is not advisable.

This valve only increases the resistance of the pump and can lead to cavitation—the collapse of bubbles formed due to a local reduction in the diameter through which the water passes.

Cavitation leads to the destruction of the impeller (roughly speaking, the filter rotor blades).

Avoid filters with this feature or simply do not use it.

Filter canister volume

This is also an important filter characteristic. The canister/flask is filled with filler, and the more filler there is, the better. Inspect the canister before purchasing.

It is now very fashionable to make as many compartments and additional plastic cells as possible, which, of course, is done for the convenience of servicing the aquarium, but eats up the useful volume of the canister.

So, out of a 6-liter volume, only 3-4 liters may remain for the filler itself. JBL CristalProfi greenline filters are distinguished by their large cells.

I prefer filters without additional cells and compartments so that all the space in the filter is used exclusively for the filler (Eheim Classic version).

But if there are flasks inside the filter, the filter can only work properly with them. That is, if you have purchased a filter with compartments, you must use them.

Presence of a UV lamp

Sterilizing water with a UV lamp is quite useful, but with a lamp power of several watts, it loses its meaning.

So, this is more of a “why not” addition. Therefore, you can safely choose a filter without a UV lamp. If you really need one, the lamp built into the filter will not be enough.

Filters with UV lamps:

Presence of filler in the kit

Pay attention to this, because it is the filler that plays an essential role in the filter's operation. Without it, it is just an empty container that circulates water. If the filler is not included with the filter, it must be purchased separately. The same Eheim Classic series filters can come with or without Eheim Substrate Pro filler.

Presence of taps on hoses

They greatly simplify aquarium maintenance. If the faucets are not included, buy them right away; they will make maintenance much easier. Don't buy Chinese faucets, buy German Eheim faucets, detachable, two pairs for each hose.

My Chinese faucets came apart in different directions when closed. Imagine if they had been connected to an aquarium? Everything would have been on the floor. And that customer has a 600-liter aquarium.

• Internal filters come with a short hose that attaches to the filter outlet. It is used to suck air from outside into the filter. It can be used if necessary; it is not a mandatory component of the design. Very often, Aquael Fan series filters are used together with an air suction hose.

It may not be obvious to some, but a filter is a piece of aquarium equipment that runs continuously. It should not be set on a timer or turned on only when necessary. The filter should always be running.

Types of filter media

Mechanical filtration

It consists of spongy materials. As the porosity of the material increases, it includes: synthetic winterizer, fine-pored sponge, large-pored sponge.

Synthetic padding is a fine-pored material that traps the smallest particles from the aquarium water.

It is usually used in specific cases: when a suspension has formed, the water has turned green, something cloudy has been added to the aquarium, the substrate has been replaced — in general, synthetic winterizer is used after some work has been done in the aquarium.

In addition, there may be fish in the aquarium that constantly stir up the water, creating visual clutter and reducing light penetration into the water.

• In such cases, synthetic padding can be kept in the filter on a permanent basis, but it must be washed weekly so that the filter's water flow does not weaken.

• Synthetic material is not durable; it can last for 2-3 washing cycles, after which it must be replaced.

Available in several formats: round or square plates for a specific filter model, or large slabs from which you can cut a plate for your filter model.

New filter models are often made in such a way that the synthetic padding cannot be cut out of the plate and can only be purchased in branded packaging. By the way, you can also pay attention to this nuance when buying an external filter — operating costs.

Fine-pored and coarse-pored sponges are a durable material for filtering water from large and small particles (not suitable for the smallest, dusty particles; synthetic padding is needed). Used to clean water from mechanical suspension in an aquarium.

They are sold in sheets or also for specific filter models. For modern filters, manufacturers make their sponges in such a way that it is almost impossible to cut them out of the sheet, so you will have to buy factory-made ones.

Sponges of different porosity can be used simultaneously in one filter.

Sintepon, large and small sponges CAN be washed with tap water, but only if you have biological filtration in addition to mechanical filtration. If there is no biological filtration (which is basically wrong, but extremely common), only 30% of the mechanical filter filler can be washed with tap water. The rest should be washed with water from the aquarium.

Note: if you rinse the sponges in a bucket of aquarium water, you can then use this water to water your plants in the garden, and they will thank you with their beautiful flowers.

Ceramic rings/balls are a filler used only in external filters to break up the inflow into the filter.

Water from the aquarium enters the filter in a powerful turbulent stream, which must be broken up into a laminar, uniform, and weaker flow so that the biological filter media is washed evenly by the aquarium water.

For this purpose, ceramic balls are used, which are placed at the very bottom of the external filter. They can be washed with tap water.

Some ceramic balls are made porous so that they combine mechanical and biological filtration. It is better to wash such balls with aquarium water.

Biological filtration

Filler in which special bacteria colonize. They process the waste products of fish and bacteria at a biological level.

During the life of the aquarium, toxic substances are released into the water: ammonium/ammonia and nitrites. The biological filter processes these toxic substances, making them harmless to the inhabitants of the aquarium.

In aquascaping, biological filtration is not always given due attention, thinking that soil and plants are sufficient (they are also biological filters), but the more you push your planted aquarium (more fertilizer, CO2, and light), the higher the chance that algae, the worst enemy of any planted aquarium, will show up when ammonia or nitrites appear in the water.

Highly porous fillers are used as biological filters, the main characteristic of which is the total surface area for bacteria colonization. This is usually indicated on the manufacturer's label. The most common biological fillers are:

Chemical water filtration

In addition to sponges and biological balls/rings, chemically active sorbents (absorbents) can also be placed in the filter.

These include:

• absorbers of nitrates, phosphates, silicates, ammonium, nitrites;

• fillers for increasing/decreasing dKh, dGh, pH.

Chemical fillers are different in that they are added temporarily. After they have exhausted their potential, they are removed from the filter and replaced with new ones or other fillers (biological or mechanical).

Activated carbon is used when it is necessary to reduce the concentration of carbon dioxide (increase pH), remove excess organic compounds dissolved in water, and remove yellowing from the water.

In planted aquariums, activated carbon is always used during the start-up phase of a new aquarium for the first month. During this period, 80% of the external filter's capacity is reserved for activated carbon.

Hardness level – 5–15 GH; Red neon

Fillers for changing dKh and dGh in planted aquariums are used quite rarely.

When keeping them in groups, experts recommend providing shelters so that females can hide from persistent suitors.

Other chemical fillers are used as needed, based on water tests.

The temperature of the aquarium contents should be between 23 and 25 degrees Celsius, but the creatures can withstand fluctuations down to 18 °C.

• ceramic rings for breaking the flow in the aquarium;
• biological filler

• 1 large-pored sponge
• acidity (pH) – 6–7.

The cockerel prefers dim light and slow currents

Install additional aeration. If this is not possible, direct the flow from the filter towards the water surface.

If this is not possible, install the internal filter at the height of the aquarium wall so that the water flow from the filter breaks the surface of the water, but the pump does not suck air from the surface.

When turning off the external filter for a long time, the procedure is the same: open the filter, rinse the filler with aquarium water, plug the filter back into the outlet, and create additional air saturation in the aquarium.

Regardless of the type of filter used, after cleaning, it is necessary to add nitrifying bacteria, for example:

In a planted aquarium, good filtration is not just about clean water, but a stable environment for plants and fish. The filter removes debris, processes harmful substances, and helps maintain balance, but it is not worth pumping the water too much — plants need peace and quiet. The main thing is to find a happy medium: the filter should cope with the load, but not create turbulence in the aquarium. It is good if it works quietly and does not require constant intervention.

Filter for your aquarium with a volume of up to 30 liters

ADA superjet ES 150

Pros:

• Full-fledged external filter
• Large canister volume
• Design
• External pump, which makes it easy to clean
• Spin pipe included

Cons:

• Rigid suction pipe design
• Small slots for water to enter the suction pipe
• Cost

An ideal filter in every way for aquariums with a volume of up to 30-40 liters, but it is much more expensive than all of its competitors, which are not really competitors, because although they are cheaper, they are inferior to the filter from the Japanese manufacturer in all respects.

Eheim Classic 150

Pros:

• Full-fledged external filter
• Large canister volume
• Tubes included
• Pump power
• Cost (compared to the ADA filter)

Dennerle scapers flow

Pros:

• External
• Sufficient amount of filler
• Lilipipe included
• White color (I am always in favor of stylish, new solutions)
• Cost

Cons

• Rigid pipe design, which makes it difficult to release air after cleaning the filter
• Hanging, not fully external

Aquael fan mini

Pros:

• Design
• Sufficient pump power
• Cost

Cons:

• Small volume for filler material
• Internal design
• Few slots on the suction side

Aquael Versamax FZN-1

Pros:

• External (hanging)
• High-quality assembly

Cons:

• “A lot of plastic” inside the filter (I always remove it to free up more space for filler material)
• There are problems when restarting the filter after cleaning

In a herbarium, filtration plays a secondary but very important role. Its main task is not to remove debris, but to create a stable environment where plants will feel at home.

Remember that your goal is a clean, transparent aquarium with lush greenery. You don't need a powerful pump that creates a storm to achieve this. It is much more important to ensure uniform, calm water movement so that nutrients reach every leaf and waste is sent to the filter in time.

Do not strive for complete sterility. Some processes, such as the decomposition of organic matter, help plants. The filter should be a reliable assistant in maintaining a delicate balance between cleanliness and the natural life of your underwater garden.