Pool: win the war against algae by planting now

I see it every year, at the turn of winter and spring. You look at your water feature, the water is still cold, the surface is calm. You tell yourself it’s urgent to wait. Yet, beneath this apparent tranquility, a real invisible battle is brewing.

Algae, those formidable opportunists, are always the first to "get out of bed." If you wait for warm weather and warm water to react, the war is already lost. To win the season naturally, the only solution is to take action immediately. Here’s how to do it.

1. The maintenance sprint in March 🏃♂️

You need to understand a basic rule of aquatic ecology: microscopic algae and filamentous pond algae need very little light and a slight warming to thrive. They wake up long before your majestic water lilies or shoreline plants.

During winter, organic matter has accumulated and started to decompose. This process gently restarts the nitrate cycle in the pond. If no plants are awake to consume these nitrates (which are pure fertilizer), the algae will feast on them. It’s simple math. To succeed at pond maintenance in March, you have to beat them to it.

2. The shadow army: rely on hardy oxygenating plants 🌿

The strategy is simple: introduce now, on a nice mild day, plants that can grow in cool water.

Beware of tricky weather! Don’t bring out your tropical or delicate plants too early; the Ice Saints are still far off. Focus on our "shadow army," the native and ultra-hardy oxygenating plants like Hornwort or Elodea.

They will literally pump nutrients from the water at the first rays of sun. This is the very essence of our approach, explained in our article on the role of oxygenating, floating, and shoreline plants in your pond.

We don’t fight algae chemically; we starve them biologically.

👉 You can already populate your pond bottom with our Hornwort Cuttings / Bottom Plants.

3. The spring trap: beware of commercial fish food 🛑

This is the classic mistake of the first warm days. You see your fish coming up near the surface, you feel tender, and you throw a handful of pellets. A monumental mistake.

The water is still too cold, your fish’s metabolism is slow, and their digestion is not optimal. Uneaten pellets will sink, decompose, and become immediate fuel for the algal bloom.

The perfect alternative: live fish food 🦐

If you really want to please your scales without ruining your balance, choose live fish food. Daphnia, worms, or small aquatic prey. The advantage is incomparable: if the fish isn’t hungry today, the live creature doesn’t pollute. Even better, it lives its life, reproduces in the pond, and provides a "fresh" pantry waiting for the right moment.

4. Water lice for ponds: your late-winter cleaners 🍂

If there is one ally to introduce at the end of winter, it’s them. Dead leaves fallen in autumn have been softened by frost and soaking. This is the favorite meal of water lice for ponds (or freshwater water lice).

These small detritivorous crustaceans are incredibly hardy and active even in very cool water. They will attack decomposing leaves and winter biofilms before this organic matter turns into nitrates.

👉 To understand their essential role throughout the year, reread our complete guide: All about water lice.
👉 Ready to recruit your cleaning battalions? Discover our Water lice.

5. The praise of laziness in the face of nature’s awakening 🧘

Finally, I invite you not to overdo it. End-of-winter maintenance should be gentle. Don’t empty everything, don’t scrub your liners raw. Don’t disturb this subtle awakening.

If filamentous algae in the pond are already present, arm yourself with patience. You can remove them manually by winding them around a bamboo stake, but don’t forget they often shelter precious microfauna (our famous live food!). Let your new hardy plants do their job of spatial and nutritional competition. Nature has its own rhythm; let’s learn to listen to it.

To your late-winter plantings, and long live Low Tech!

Mattier