The magical power of plants

When we talk about the unique power of plants, we generally think of photosynthesis, which is their singular ability to capture CO2 and release oxygen under the effect of light.

But in an aquarium, while the emission of oxygen is always good to take, it is not the main thing. A simple air pump can achieve roughly the same result, albeit at the cost of a bit of noise.

For the aquarist and pond enthusiast, there is a much more concerning problem.

For all living things that are found in water die one day, or produce waste daily. And all of this waste contains nitrogen.

This nitrogen, as we know, will first be found in ammoniacal form, then in the state of nitrites (both of these forms being toxic), and finally will become various nitrates.

These nitrates are less toxic than the forms that precede them, but still.
Beyond a certain threshold, they become harmful and can kill fish and invertebrates.

This is the problem, for example, with our drinking water, which is becoming less and less free of nitrates.

At the tap, the acceptable limit is set at 50 mg/l. It is sometimes exceeded, and 20 to 40 mg/l has unfortunately become very common.

Nitrates accumulate in the water, and nothing comes to remove them.

"Above all, not the filter, which has no utility in the nitrogen cycle, contrary to popular belief and commercial discourse. The filter allows for the transformation of ammonia into nitrites, then into nitrates, exactly as it happens on its own in its absence! If it is not there, the work is done by the same bacteria in the free water, the soil, and all the surfaces of the aquarium or pond."

And, with or without a filter, the transformation of nitrogen stops there, once the nitrates are obtained.

"Never has a filter reduced the amount of nitrates by a milligram."

These harmful compounds therefore accumulate, and their levels only increase over time if nothing is done.

Of course, we advise you to carry out "water changes," specifically to remove those nitrates.
But if these changes are made with tap water that itself contains a large amount, it is useless. It can even, if the tap water contains more than the aquarium, increase the level!

"This is where plants and their magical power come into play."

They are the only living beings that can use nitrates for nourishment. When a plant grows, it assimilates nitrates.

"When it stops pushing, it no longer captures it, or even rejects it through its dying leaves."

"So we need plants that grow, and for that... light."

It is thus the light, through the plants, that eliminates the nitrates.

Not the filter, but the lighting!

Without plants, algae (including green water) or mosses, the nitrate levels would only increase.

With many plants that receive a lot of light, the nitrate level can approach zero. Making water changes as recommended by the manual then becomes heresy, since you are replacing nitrate-free water with water that contains too much.

If we understand the ecosystem through plants, we therefore dispel many preconceived ideas (and widely maintained) about filtration and water changes.

An aquarium without a filter and very well-lit, even with a high density of fish, can therefore end up almost without nitrates.

And when the plants are too large, you cut them and take them out of the water. The nitrogen thus leaves the aquarium or the pond, but this time in the form of plant tissues.

Animals have only plants and other animals they eat as their source of nitrogen (and thus of proteins).

Nitrogen enters the aquatic food chain through plants (including algae), which are the only ones capable of retrieving it, among other forms as nitrates.

The deep understanding of these rules that govern the living often allows, as we can see here again, to contradict those of the manual!