We are a family-run business, super passionate about delivering the best. Specialising in unique premium quality garden, pond and home products, we believe you deserve the ultimate performance to suit your needs. That’s why we invest time and attention into adding powerful, naturally derived active ingredients that make for stronger, more effective solutions and happy customers.

Call us on 01246 240880

How to Clear Lake Water

25th May

Lakes can create a thriving ecosystem in gardens. Filled with an abundance of wildlife and plants, they not only add to the aesthetic of a garden but create a valuable habitat for some of the UK’s most common insects, amphibians, and birds. 

However, as they usually don’t contain a filtration system and have slow-moving or stagnant water, common problems such as algae and green water can quickly develop. Whilst these problems don’t cause an immediate threat for the wildlife, over time they can begin to deteriorate the condition of the pond and force wildlife to look for a more compatible habitat. 

What causes green water and algae in lakes? 

Lakes have a particularly large surface area which leaves them open to the elements and makes it very easy for plant debris to make its way into the water. Over time fallen leaves and twigs sink to the bottom of the lake and start to decompose. As they decompose, they add to a layer of organic matter, or sludge, on the bottom of the pond. This sludge then acts as a food source for algae and green water, leaching out high levels of nutrients into the water. In ornamental ponds with filtration systems, this is less of an issue. The pump and filter can physically remove the sludge and in turn the food source. If left untouched, this sludge can begin to turn anaerobic and over time, produce hydrogen sulphide which can give off a rotten egg smell in water. This gas can pose dangers to wildlife in high enough concentrations. 



How can you prevent organic waste from building in ponds? 


As lakes have a large surface area, it is easy for organic debris to enter the water. Therefore it is difficult to prevent organic waste from building. There are however a couple of things that can be done. For example, if you have large trees or plants surrounding the lake, ensure they are regularly maintained. This will prevent dead plant materials from entering the water.

How can you clear green or murky lake water? 

If prevention is not an option for you and your lake is already green or murky, there are a couple of things that can be done to clear lake water. 

Pond Plants 

The same nutrients that feed the green water, blanket weed and duckweed also feed pond plants such as lilies. Consider adding pond plants both in the marginals and in the deeper parts of the lake. Plants such as lilies will help to absorb nutrients and also create a layer of cover on the surface of the lake from the sun. Reducing the amount of UV that enters the lake will reduce the growing conditions for algae and green water. Discover a beginners guide to pond plants here.


As lakes typically have slow-moving or stagnant water, it is very easy for nutrients to collect on the bottom of the lake and begin to build. Adding a simple form of aeration such as a solar fountain can keep the water moving. This will also increase oxygen levels in the lake. 


The most cost-effective treatment for green or murky water in lakes is a bacterial treatment such as Envii Lake Klear. Using a blend of beneficial bacteria, Envii Lake Klear binds together and sinks the particles that cause green water to the bottom of the lake. Once there, they begin to break down the particles and sludge converting them into oxygen and CO2. These are then absorbed by the pond plants. Breaking down and digesting this sludge also prevents harmful hydrogen sulphide from being released into the pond. The bacteria remain present in the water continuing to break down organic waste and keeping water clear. Regular treatments of Envii Lake Klear help to keep water clear and promote thriving ecosystems for wildlife. 


How to clear algae in lakes? 

You will usually find that you either have green/murky water or an algae or weed such as blanket weed or duckweed. This is because the algae and weeds use the same food source as green water and as they are stronger, they are able to outgrow the green water spores and in turn, prevent the water from turning green.  

One common approach when clearing algae from ponds is to physically pull out the algae. Whilst this provides a quick solution, it is also a short-term solution and can compound the problem going forward. Once algae is pulled from the water, it breaks and releases new spores into the water. These spores then grow quicker and more aggressively than their predecessors and in some cases, blanket weed can return within days. 

Whilst algae can be killed and prevented using a bacterial treatment such as Envii Lake Klear, a quicker option is to use a treatment such as Envii Algae Klear Xtra to directly target and kill the algae.  





Related Products

  • Front view of Envii Lake Klear

    Envii Lake Klear

    Clears green water and sludge in large ponds and lakes.
    Add to Basket
  • Pond Algae Treatment - Envii Algae Klear Xtra

    Envii Algae Klear Xtra

    Kills submerged algae and blanket weed.
    Add to Basket

Related posts

22nd August

11 Reasons Why Your Pond Isn’t Clearing

Find out more
17th August

Tricks to Prevent Green Pond Water

Find out more
26th February

Pond Klear – The Green Pond Water Treatment Revolution

Find out more

Share this page

About the author

Olivia Ball

Marketing Manager

Olivia is our resident plant lover. She literally lives for plants. No really, she’s vegan. But outside her passion for plants, Liv is all about adventures. Her most cherished adventures include travelling the lands of Australia and Bali, skydiving and performing at the Sadler’s Well Theatre in London. However, when she’s not plotting her next big happening, she’s busy planning creative and engaging content.

Notify of

Inline Feedbacks
View all comments