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11 Reasons Why Your Pond Isn’t Clearing

22nd August

Discover 11 common reasons that explain why your pond water isn’t clearing, even after using an Envii pond product. Each followed with a simple solution.

Jump to:

1. Water Volume  2. Overdosing  3. Pumps & Filters  4. pH  5. High Pond Nitrates

6. Well/Boar Hole  7. Pond Plants  8. Grass  9. UV Lights  10. Wrong Product  11. Patience


How To Calculate the Volume of Your PondHow to Clean Your Pond FiltersHow to Check Your Pond Filters are Working

Pond Water Volume Dosage

Water volume is one of the single most important things every pond owner should know about their pond. Without it, it can be difficult to know if the pond is being treated correctly. In fact, more often than not, not knowing or having the incorrect pond water volume is the most common reason for people to see little to no progress in the water clearing. So, how can you get the correct pond water volume measurement?

How do you measure a pond’s water volume?

To measure your pond, all you need is a measuring tape. Measure the width, length and depth of your pond and multiply the measurements together. Then, multiply the answer by 1000 and the final figure will be the volume of water in your pond. Alternatively, you can use or quick and easy pond water volume calculator.

Again, knowing the volume of water in your pond is very important. Our products can’t be overdosed but without knowing the volume of water in their pond, pond owners will often UNDERdose our products. Meaning they aren’t treating it enough to see the results or the best results.

Video: How To Calculate the Volume of Your Pond


We know what you’re thinking. We just claimed our products can’t be overdosed. This is 100% true. No amount of Envii pond products will cause harm or damage in a pond because they’re 100% natural.

However, they can be overdone. If there was a clear pond for every time someone poured a whole bottle of Pond Klear into their pond (without knowing their pond water volume), then we would be constantly out of stock! However, that’s not how it works. While it might seem like a good idea to add the whole contents of a Pond Klear into your pond, it’s actually counterproductive.

Is too much beneficial bacteria bad for your pond?

You see, algae are a food source for beneficial bacteria. If your pond is filled with too much bacteria at any one time, they fight and compete with each other until their numbers are low enough to focus on the food source.

Which means pouring a bottle of Pond Klear into your pond water is actually just wasting a lot of beneficial bacteria. This goes back to knowing your pond water volume so you can be sure the correct amount of treatment to apply to your pond.

Pumps and Filters

Pumps and filters are another reason your pond might not be clearing. (If you don’t have a pump and filter, then you have a natural pond and the ideal treatment for filter-less ponds is Natural Pond Klear). The job of a pump and filter in your pond is to assist the water system in cleaning the physical matter in your pond such as debris, dead leaves and organic waste.

How often do you clean your pond filters?

Is it regularly? If not, this can be a reason our pond treatments don’t seem to be working. It’s because your filter system is pumping dirty water back into the pond. Therefore, green water and blanket weed causing algae continue to have a food source to thrive in your pond.

Depending on the condition of your pond, we recommend cleaning your filters every couple of days if they’re extremely dirty and weekly if they’re moderately dirty. Check out this video for the best way to clean your pond filters.

Video: How to Clean Your Pond Filters

Pond Filter and Pump Quality

If you do clean your pond filters regularly, then it simply might not be working efficiently. Watch the video to the side for a simple hack to check if your pond filter is working.

If you’re relying on a submerged pond pump with a built-in filter, then you’re relying on something that’s poor quality and only as good as having a pond pump alone. Consider installing a filter which has both mechanical and biological pond filter components.

Video: How to Check Your Pond Filters are Working

pH Levels

When your pond pH is not balanced, being too high or low, it will affect how the bacteria perform at removing algae from the water. When the pH is too high (alkaline) it can slow the rate at which bacteria both consume algae but also replicate. While also allowing algae to grow more vigorously, making it difficult for bacteria to control.

What pH should my pond be?

Much like how bacteria perform better in certain temperatures, they also require certain parameters to work effectively. Measure your pond’s pH with a testing kit, we recommend a pH between 7.5 to 8.5.

If you pond pH is higher or lower than this, you should use a pond pH buffer such as Pond Equaliser first, to balance and neutralise the pH to the recommended reading before using a pond clearing treatment.

High Nitrate Levels

Nitrates are the algae’s food source. If the nitrate levels are high and not being reduced, algae have an unlimited supply of food and can grow faster and stronger than the bacteria can suppress it.

How do high nitrate levels affect a pond?

Algae thrive in ponds with high nitrogen levels. Nitrates are algae’s source of food. When levels are high, algae have an unlimited supply of food to grow faster and stronger. So much so that the beneficial bacteria will struggle to keep up with the growth to suppress it.

Similar to pH levels, you can test your pond nitrates levels with a testing kit. The recommended measure for nitrates in a pond should be between 20 and 60ppm.

If you find that your pond nitrates levels are high, that will be the reason your pond water isn’t clearing. Treat your pond with Nitrate Klear to reduce and remove algae’s food source. Beneficial bacteria will then grow in sufficient numbers to eliminate algae.

Related Products

  • Front view of Envii Nitrate Klear - water quality treatment Envii

    Envii Nitrate Klear

    Removes harmful nitrates from pond water.
    Add to Basket
  • Front view of Envii Pond Test Strips Tube

    Envii Pond Test Strips

    Easy to use Pond Test Strips measuring 5 key water parameters
    Add to Basket

Well or Boar Hole

Ponds that are re-filled with water from a well or borehole close to arable farming might also struggle to clear their pond because of nitrates. This is because nitrogen from farm crop fertilisers leaches into the ground, contaminating the water course and pond.

Again, to eliminate this problem, first treat your pond with Nitrate Klear. Making sure your pond pH and water parameters are balanced before starting with our beneficial bacterial treatments.

Recently Added Pond Plants

Nitrogen can also be introduced into a pond through newly added pond plants. Plants bought from garden centres and plant nurseries are typically fed with a nitrogen fertiliser to keep them healthy. This fertiliser then leaches out into the pond and causes an increase in nitrate levels in the pond.

Luckily there’s a simple and straightforward solution for this. There’s no need to get rid of your pond plants. Simply sit brand new pond plants in a bucket of tap water for one week before adding them to your pond. This allows all the nitrogen-rich fertiliser to leak out the plant so you can safely add them to your pond.


Another plant that can affect the clarity of your pond is grass. You might be treating your pond correctly, having working filters and your pond chemistry is balanced, but your water is still green. So what’s the reason your pond isn’t clearing?

In some cases, when a pond is next to grass or grass falls into the pond when cut, it can actually stain the water. Although this depends on the size of the pond and the amount of grass, it does happen. If you realise this might be the problem, you need to do 20-30% water changes for a couple of weeks to get rid of the natural dye.

UV Lights On

One question we frequently get asked by customers is whether it’s okay to leave the UV filters switched on in the pond while using our treatments. UV Filters or ‘clarifiers’ expose high levels of ultraviolet light to single-celled algae. Working to destroy their DNA and killing them. However, this same ultraviolet light also kills off beneficial bacteria in the pond. Which are essential to prevent the build-up of organic waste and algae.

Many customers have used our products to clear a pond that had been using UV filters. Suggesting that beneficial bacteria are arguably better at keeping your pond clear. In fact, some customers say they never bothered turning the UV lights back on.

Our pond products do contain strains of bacteria with a high tolerance for UV rays. However, if you do use UV filters in your pond, we advise that you turn them off for at least 48 hours after applying our beneficial bacterial products to your pond. This allows time for the bacteria to anchor themselves within the pond, multiplying in sufficient numbers to effectively remove algae.

Wrong Product

Sometimes the answer to why your pond isn’t getting clear is simply that you’re using the wrong product. Many people often mistake submerged algae for blanket weed or mistake green water for submerged algae.

Make sure you correctly identify what your pond problem is first before you commit to buying a treatment. You can read any of our pond blogs to help you better understand pond problems or alternatively, you can give us a call for more technical advice and support.


Sometimes if your pond isn’t clearing after treatments, it’s just a case of patience. How fast your pond will see results depends on a range of things. Including the points mentioned in this post. However, the most important things to consider are the size and condition of your pond.

How long does it take for a pond to clear?

With continued regular treatments, your pond can see results from as early as 2 weeks. Again, with emphasis on the severity or condition of your pond. Typically, though, most ponds can expect to see results between 6 to 8 weeks. If this seems like a long time, remember that you’re using a natural, biological product, not chemicals. So, results will take some time, especially for really bad ponds.

If you have been using a product regularly for longer than this period of time and none of the points we have mentioned apply to your pond, give us a call for tailored advice and technical support.

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Cassie Campbell

Hi I recently brought lake clear 200sm off of Amazon on the 26th of May and put it into our pond.
We moved to a house last year which has a 68 foot long by 38 foot wide at the longest points it shelves but I’m not sure of where and how as I can’t see through the water it’s very green it’s 4 foot deep at highest point but it’s a foot down from the top right now. It o my has a pond pump it has no filter. I have planted 8 lilies and a mass of other plants to try and help clear the water.
I’d say it’s marginally clearer after using your product.
I’m just wondering if you could suggest what I can do next to try and clear the green water more.
There are many fish in the po d who all
Seem very healthy.
Many thanks Cassie