Can we really do without a filter? The secret of the living nitrogen cycle

If I began fishkeeping in 1981, it was in 2004, following experience and the discovery of the concept of the poubellarium, that I theorized and started to publicly assert that the motorized water filter was unnecessary in a well-thought-out aquarium. People looked at me like I was an alien. For many, it was total heresy. The fishkeeping trade at the time hammered into us that a powerful pump was needed, circulating three to four times the tank volume per hour, or else our ecosystem would collapse in a few days.

Yet, my tanks ran wonderfully. The water was crystal clear, the fish in great health, and the plants lush. Not a hint of a motor.

Today, I would like to share with you my experience as a pioneer of Low Tech. I will explain why the filterless aquarium is not a fancy idea of a dreamer, but rather the logical outcome of a true understanding of the natural nitrogen cycle.

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1. The historical anecdote: when the electric train dives into the water 🚂

To understand our dependence on the filter, we must go back in time. Did you know how the first motorized pump filters for aquariums were born in the 1960s?

They were not invented by biologists seeking to improve fish life. They are the result of diversification by a famous German company… that made electric trains and toys! They had the small motors, saw a budding market, and created the need.

The mechanical filter is therefore, above all, a triumph of industrial marketing over biology. Patience and observation were replaced by an electric plug.

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2. The true home of bacteria (spoiler: it’s not the plastic box) 🦠

The number one argument of filter sellers is "biological filtration": the filter would be the essential home of good bacteria.

This is biologically false. Nitrifying bacteria (those that transform toxic ammonia into nitrites, then nitrates) do not live "in" the suspended water, nor exclusively in the ceramic rings of your filter. They attach to surfaces.

In a natural aquarium, these bacteria colonize every grain of sand, every glass pane, every root, every leaf. Remember the old "undergravel" filters of our grandparents! They understood one fundamental thing: it is the soil and the decor that have always been the true engines of the aquarium. The equivalent of your filter is your soil. The plastic box is only a tiny surface compared to the vastness of your decor.

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3. The nitrate paradox and the CO2 problem 💨

The modern filter suffers from two huge flaws that are often kept quiet.

The first is the nitrate factory.
Your filter, like the bacteria in your soil, is very good at transforming toxic waste into nitrates. But then? It stops there. It saturates your water with nitrates (which encourage algae), forcing you to do massive water changes. In my heavily planted tanks, I measure 0 nitrate. Why? Because my plants (emerged, floating, fast-growing) are the only true way to consume these final nitrates.

The second is the loss of CO2.
A filter stirs the surface. This excessive stirring causes degassing: it drives the precious CO2 naturally present in the water into the open air. By doing this, you deprive your plants of their main fuel, thus weakening the only true purification power of your tank.

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4. Protecting life and rethinking organic load 🐌

My refusal of the filter is also an ethical choice to protect life. I have lost count of the number of fry, tiny shrimps, or water lice I have seen crushed by rotors or trapped to death in synthetic sponges. Without a filter, the microfauna swims and reproduces in peace.

And do not believe the myth that a tank without a filter can only hold "very few fish." The organic load is not linked to the power of a pump, but to the ratio between your plants and your fish. Many vigorous plants can support a good population, provided common sense is applied.

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5. My method for a smooth transition (weaning) 🛠️

If you already have a filtered tank and want to take the step to a natural aquarium, do not unplug everything overnight! Here is my 4-step method for a gentle weaning:

Step 1: prepare nitrate absorption

Plants do not replace the filter’s role (they do not transform ammonia), but they are essential to absorb the final result: nitrates. Before starting the transition, boost your plant mass. Add massively fast-growing plants (Hornwort, Elodea) and surface plants (Salvinias, Large duckweeds) which are the biggest consumers of pollution.

Step 2: reseed with microfauna

The filter sucked up and accumulated physical waste. Without it, detritivores will do this meticulous work of breaking down waste on the soil. Introduce Water lice, Ostracods, and make sure you have a good team of snails (Malaysian Trumpet Snails to stir the sand, Ramshorn snails for the leaves). They will colonize the decor and replace the mechanical action of your blue sponges.

🔗 the Starter ZollaBox (Microfauna and Bacteria)

Step 3: gradual weaning and the golden rule of removal

Do not cut the pump suddenly. Over about 15 days, gradually reduce your filter’s flow (if adjustable) or slightly block the outlet. This slowdown will allow the bacteria present in your soil and on your decor to multiply naturally to compensate for the weakening of the microbial population in the filter.

⚠️ THE GOLDEN RULE: after these 15 days, when you stop the motor for good, you must immediately remove the filter from the aquarium.
A stopped filter left in the water will quickly become an oxygen-free environment. The filter media, trapped waste, and especially billions of bacteria will die very fast and release a massive toxic pollution into your tank. Stop it, take it out!

Step 4: observation rather than chemistry

Put away your anxiety-inducing chemical test kits. Watch the living! If your fish breathe calmly, if your snails (Malaysian Trumpet Snails) stay quietly in the soil instead of fleeing to the surface, it means the natural nitrogen cycle has successfully taken over.

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Conclusion

Choosing "without filter" is ultimately freeing yourself from a technical constraint to reconnect with observation. It is accepting to trust nature and your soil, which have millions of years of lead over our plastic pumps.

If I could do it at a time when everyone thought I was crazy, you can do it today, supported by the Aquazolla community. Unplug the plug, remove the box, and watch life settle in! 😉