How to Clear Green Pond Water

Green pond water has to be the number one challenge new pond owners come across. Along with what fish to stock and what plans to use, keeping pond water clean and clear is the most important consideration.

That’s what we’re going to tackle today.

As pond experts with decades of experience, Closer Pets will share the causes, effects, and remedies for green pond water.

What causes green pond water?

The primary cause of green pond water is algae. These are tiny single cell organisms that live in water.

Not all of them are green, they come in all kinds of colours, so if your water is more a brown or a red colour than green, it is still likely to be algae.

Algae are carried in the wind and land on water. They can also be dropped by birds and find their way to water in many ways.

As long as the pond has access to light and is nutrient rich, algae will grow.

Algae will readily grow in ponds with excess nitrate. Nitrate is generated by decomposing fish food and plant life and fish waste.

Do algae cause harm to the pond or to fish?

Algae growth is a natural process. In small amounts, it poses no risk to your pond or fish.

Unfortunately, algae don’t know when to stop and will reproduce non-stop.

Once it covers the pond, it will restrict sunlight getting into the water. This can keep the water cool but also interrupt the natural oxygenation process.

It also ruins your view of the fish, which is equally annoying, just for different reasons.

How can I get rid of green pond water?

Getting rid of green pond water is a two-stage process. You first have to get rid of the cause of the algae. Then you have to get rid of the algae itself.

First, tackle the cause.

Algae growth is accelerated by lots of sunlight and nutrients in the water. As fish need sunlight, it’s easier to tackle the excess nutrients.

Keep your pond clean – Remove dead foliage and plants regularly to prevent them decomposing in the water. Decomposition creates nutrients for algae, so removing as much as possible removes a food source.

Tweak your feeding – Excess fish food in the water is a prime cause of algae. As the food breaks down, it releases nitrates in the water, which feeds the algae. Monitor feeding and tweak levels according to your fish stock to avoid excess.

Plant around the pond – Adding surface plants around the pond will take some of the sunlight and nutrients from the algae, slowing down their growth. Plants can also help oxygenate the water, which is an added benefit.

Use a pond test kit regularly to monitor nitrate levels in the water. Too much and you risk algae growth.

Use a pond filter and clarifier

A pond filter won’t remove algae from the water as they can flow through filters, but they can remove other debris from the water.

It’s the clarifier, often with a UV light, that helps remove algae.

Get the right size pond pump and filter for your pond and ensure it has a UV light as part of the filter.

As algae passes through the UV, the cell is damaged, preventing reproduction.

Over time, along with treating the root cause, your pond water should gradually clear and stay clear.

Cause and effect

When tackling green pond water, it’s vital you tackle both the cause and its effect. Otherwise, you’ll never rid your pond of algae and will be forever tackling it.

A pond filter and clarifier on its own can clean up your pond water. But, unless you tackle the cause of algae growth, it will always be a battle between two forces.

Remove the cause of excess algae and your filter and clarifier will have a much easier time keeping your pond water clean and healthy.

Chemicals and water treatments

There are a number of chemical additives and water treatments you can use to treat green pond water but we would recommend against them.

One, unless you treat the cause of algae, you’ll be in the same position as using a clarifier.

You’ll add water treatment, enjoy clear pond water for a while and will then have to repeat the process once algae return.

Two, we try to recommend against adding chemicals to water wherever possible. While the chemical may not harm the fish, we would much prefer pond water to find its natural balance without the use of chemicals.

Three, water treatments can be expensive. You’ll be using quite a lot of them depending on how bad the algae growth is.

It is far cheaper and better for the fish to tackle the root cause as much as possible and use a simple pond filter and clarifier to keep the water clean.

No chemicals, no risk to fish and a clear view all year round without using chemicals or upsetting the natural balance.

What’s not to like about that?

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