Building a Natural Pool (Or Hiring a Pro?)

Two scenarios await your future natural pool: a thriving ecosystem, or water that turns greener every season. The difference is decided before you break ground.

Natural pool with crystal-clear water built by Bäckahästen

Do you dream of a small ecosystem in your garden? A place where nature does the work of keeping the water clear, instead of you dosing chemicals all year round. Just glittering water, a babbling stream and drifting water lilies.

But if it is not done right from the start, green water, uncontrolled algae blooms and expensive rebuilds are waiting. Unlike a chlorine pool, a natural pool cannot be rescued after the fact with chemicals — and the worst problems only show up months after you are "finished".

This article helps you decide whether to build your natural pool yourself or hire a professional from day one.

What decides the outcome?

Algae cannot establish themselves without nutrients to live on. The goal of every natural pool is therefore to create a nutrient deficit — an oligotrophic environment. If you fail to create the conditions for that, no chemical can fix it later. An ordinary swimming pool becomes over-fertilised in exactly the same way, but chlorine kills the symptom: the algae.

In a natural pool the cause itself has to be treated: the nutrients.

The biological process

Below the surface this is nitrification. Organic matter breaks down into ammonium, which in turn becomes nitrite and finally nitrate, which the plants can use.

In a man-made system algae have a natural advantage over plants, because they can absorb nutrients throughout the entire water volume while plants only take up what is close to their roots.

Getting around that requires active filtration that locks the nutrients into the plants before the algae can establish themselves. In other words, the entire water volume has to pass through the gravel and root layer.

If the pool cannot bind nutrients as fast as they are added, they build up in the water instead — a process called progressive eutrophication. A small surplus each cycle is all it takes.

DIY: David Pagan Butler''s Bubble Pool

David Pagan Butler Bubble Pool natural pool build

The most popular method among people who want to build their own natural pool is David Pagan Butler''s Bubble Pump method. This type of natural pool looks like a traditional pool with plants in it.

It is built around a downflow filter, where a bubble pump draws water in from above, through gravel and roots that take up the nutrients. That is the idea, at least.

Pagan Butler himself devotes a large share of his own content to troubleshooting algae blooms: a tool for pulling filamentous algae out by hand, recurring episodes on why a pool suddenly turned green.

If the balance is that delicate for the inventor of the method, it is hardly simpler for someone building their first pool.

Professional: Aquascape Ecosystem

Aquascape Ecosystem natural pool built by our project manager

The AQUASCAPE Ecosystem is as close to nature as you can get, both in function and in appearance. The entire water volume passes through an upflow Wetland Filter once every hour.

Everything is as functional as it is beautiful. The babbling streams and waterfalls, for example, oxygenate the water for the beneficial micro-organisms the system depends on. The impression is a natural spring that has always been there, rather than a traditional swimming pool with plants in it.

The pre-balanced ecosystem also grows stronger every year, which means a more self-sufficient natural pool over time rather than the opposite. Maintenance is considerably lower than in other systems. So even though the investment is larger, you save time and avoid unpleasant surprises.

Which path do you choose?

When an undersized system crashes there is only one way forward: dig up liner, gravel and pipework, clean out the base and rebuild from scratch. That is the point at which many people turn to professionals.

If you genuinely want to learn how to build your own natural pool, we recommend starting with a smaller garden pond, where the consequences are far smaller.

Would you rather have it right from the start?

Book a free consultation with Bäckahästen, Sweden''s most experienced Aquascape team.

Frequently asked questions

Can I build a natural pool myself?

Yes, but the result stands or falls with the filtration. An undersized filter only reveals itself months later, once nutrients have built up and the algae take over. If you want to learn the method, a smaller garden pond is a much cheaper place to practise than a swimmable pool.

Why do natural pools turn green?

Because nutrients are added faster than the plants can bind them. Algae absorb nutrients throughout the whole water volume, while plants only take up what is nearby. If the entire volume does not pass through the gravel and root layer regularly, progressive eutrophication sets in and the water turns greener every season.

Can a green natural pool be rescued after the fact?

Not with chemicals. A chlorine pool kills the symptom, the algae, but in a natural pool the cause has to be treated: the nutrients. When an undersized system crashes, the fix in practice means digging up liner, gravel and pipework, cleaning the base and rebuilding the system from scratch.

How often should the water pass through the filter?

In an Aquascape Ecosystem the entire water volume passes through an upflow Wetland Filter once every hour. That turnover is what locks the nutrients into the plants before algae can establish themselves.

Does a natural pool need chemicals?

No. A correctly sized ecosystem maintains swimming-quality water through biological filtration, oxygenation from streams and waterfalls, and plants that outcompete the algae for nutrients.