Lower your nitrates naturally with floating plants
F. MattierIf you read me regularly, you know my passion for natural balance. Yet, I still see too many enthusiasts designing beautiful tanks or ponds while overlooking a crucial element. For me, an ecosystem without floating plants for aquariums or ponds is a system that voluntarily deprives itself of its best purifiers. Let me explain why their privileged access to resources makes them simply unbeatable against algae.
The secret of floating plants: atmospheric CO2 and unfiltered light
In the water, the battle for nutrients rages on. Submerged plants must struggle to capture dissolved carbon dioxide, often present in limited amounts. Floating plants, however, have found the loophole: they free themselves from this competition by drawing their CO2 directly from the air, where it is inexhaustible!
But that’s not their only "unfair advantage." They are also front and center for light. Unlike bottom plants, they benefit from direct sunlight or your lighting fixture without any attenuation caused by water depth or the shadow of other plants.
The direct consequence of this abundance of carbon and light? They operate at full capacity and become powerful pumps that suck nutrients from the water. This is the most effective method to reduce nitrates naturally. By occupying the surface and devouring resources, they literally cut off the food supply to algae.
Azolla: my secret weapon against phosphates
Within the large family of floating plants, Azolla is a fascinating case. It lives in symbiosis with a cyanobacterium that allows it to capture nitrogen directly from the air.
That’s where its magic lies: since it is not limited by a lack of nitrogen or carbon (both taken from the air), it can focus on the rest. It therefore draws heavily on phosphates in the water to support its growth, even if your water is very low in nitrogen! Azolla’s role in phosphate uptake perfectly complements the action of other plants. By combining it with other floating plants, you cover the full spectrum of biological purification.
👉 Discover our strain of Azolla filiculoides.
The exception of oxygenation
Be careful with a common misconception: since their stomata (the "pores" through which they breathe) are in contact with the air, floating plants release their oxygen into the atmosphere, not into the water. The exception that proves the rule is the famous three-lobed duckweed (Lemna trisulca), which lives suspended just below the surface and therefore oxygenates the aquatic environment.
Roots teeming with life: a pantry for your fry
Floating plants are not just chemical filters; they are also the heart of biodiversity in your tank. Their roots form a true "micro-jungle" suspended in the water. This dense network teems with purifying bacteria and infusoria.
This highly lively zone is not only a safe refuge for the microfauna, but also an exceptional pantry. In both aquariums and ponds, daphnia and especially fry find abundant natural food there from their very first days of life. They can hide while nibbling on the microscopic prey that proliferate there.
For fans of big polluters (goldfish, koi carp), let’s not forget the nutritional aspect. duckweed for goldfish is not just a simple snack: it is essential food and one of the best diets for these herbivorous-leaning fish. This living, healthy, and 100% free plant base is a true feast, especially if a few aphids join in to add extra protein! They love it so much that they can completely clear a pond of its duckweed during the summer. Your fish enjoy themselves and naturally regulate the surface population.
👉 Want to seed this root life? Our ZollaBox contains the perfect microfauna to colonize your floating plants.
How to manage the invasion? The art of filtering light
The downside of such vitality is, of course, overgrowth. The goal is not to completely cover the surface and plunge your bottom plants into total darkness. Think of floating plants like Venetian blinds: they should "filter" the light.
It is important to choose your species based on how much time you want to spend on maintenance. Common duckweed or Azolla spread very rapidly. If you prefer a slower pace, opt for species with slower growth and easier manual removal, such as Salvinia, Phyllanthus, or Floating frogbit.
👉 Find our strains of Salvinia and Floating frogbit (Limnobium laevigatum) in the shop.
🚨 Legal note: beware of Water lettuce!
I must make a very important reminder. Pistia stratiotes (Water lettuce) is still too often found among private individuals. This plant is now strictly prohibited in Europe. Its possession, gifting, and sale are illegal due to its highly invasive nature in our natural environments. If you have it, destroy it (by composting it far from any water source) and replace it with Floating frogbit or Salvinia, which are just as beautiful and perfectly legal.
Conclusion: the obviousness of biological simplicity
Don’t fight algae with products. Don’t exhaust yourself with massive water changes. Simply let nature do what it does best. By introducing floating plants, you offer your ecosystem a protective roof, a living pantry, and a tireless purification station.
Mattier