Green pond water is something that just about every pond owner experiences at some stage.
When your pond turns green, it’s a sign that the pond’s ecosystem is out of balance.
There are many natural ways to clear pond water, so you don’t have to take drastic action like draining your pond or using harmful chemicals.
Here are some easy ways to get rid of murky, green pond water naturally.
This post contains affiliate links. Please read the disclosure for more info.
A note for new pond owners:
If you’ve just installed a new backyard pond and the water has turned green, don’t be tempted to drain the pond.
It takes time for the good bacteria to build up in the pond, so if you drain the pond you’ll just have to start over.
You can help it along by adding natural beneficial bacteria to your pond.
As the good bacteria reproduces you’ll notice that the algae will decrease and you’ll get less algal blooms over time.
You can also try a product called pond enhancer, which contains natural bacteria along with a blue dye that is safe for fish and helps to shade the pond so the algae don’t receive as much sunlight to grow.
What causes ponds to turn green?
Green pond water is caused by an overgrowth of algae suspended in the water.
Algae becomes overgrown when nitrate and phosphate levels in the water are high.
What leads to an imbalanced pond ecosystem?
Leaves, dead plants and lawn clippings that fall into the water decompose and form sludge.
When sludge and muck builds up on the bottom of the pond, it releases nutrients into the water which provides food for algae to grow.
Too many fish in the pond
Fish waste breaks down into nitrates that algae feed on.
Many people buy too many fish for their pond, not realizing that they reproduce quickly.
Goldfish reach sexual maturity at one year of age and they can spawn up to five times a year during the warmer months. 
Koi are fast growing fish and spawn in late spring to early summer.
It doesn’t take long for a small pond to become overrun with fish, so you may need to sell or give away some of your fish.
If you’re feeding your fish too much, the uneaten food will rot and produce food for algae.
Scoop out any uneaten fish food and reduce the amount of food if it’s being left uneaten.
Feeding your fish less will also give the fish an opportunity to eat some of the algae.
Not enough plants in the pond
Pond plants help to reduce algae because they consume nitrates and phosphate in the water, leaving less nutrients available for the algae to grow.
How to get rid of green pond water
Clean the pond regularly
If you have a large pond, you can install a pond skimmer that will remove any leaves or debris that falls into the pond or get into a routine of regularly scooping out any plant matter that falls into the pond.
Use a long handled net to remove the muck and sludge that builds up on the bottom of the pond or use a pond vacuum to suck up the sludge.
Another way to reduce the sludge is to add muck reducer tablets to the pond to help break down the sludge naturally.
These tablets contain beneficial bacteria and they’re safe for pond fish.
Install a UV clarifier
UV clarifiers use ultraviolet light to destroy algae that is suspended in the water.
Using a UV clarifier is an effective way to remove heavy algae blooms in as little as five days and keep your pond free of algae overgrowth in the long term.
Increase the number of pond plants
Plants compete with algae for nutrients in the pond, so include some floating plants like water hyacinths or water lettuce (check that they’re not banned in your area), along with some marginal plants like lotus and water lilies.
Reduce the number of fish
De-stocking your pond will help to reduce algal blooms and give your fish more space to swim around.
Is green pond water dangerous for fish?
A small amount of algae is normal in a healthy pond and fish will eat the algae, but when algae becomes overgrown, oxygen levels in the pond fall quickly, which can lead to fish kills.
How long does it take to get rid of green pond water?
Depending which method you choose, it can take a few weeks to a month before you start noticing your pond water clearing. Using a UV clarifier will speed things up though.
So there are my tips for clearing green pond water naturally.
Algae overgrowth is one of the most common problems for backyard pond owners but by following the tips in this article, you should be able to get on top of the problem in a short amount of time and have a healthy, balanced pond ecosystem.
- How do UV Clarifiers Clear Pond Water?
- Garden Pond Aeration
- 6 Edible Water Plants
- Creating A Pond Waterfall
- How to Keep Pond Water Cool in Summer
What do you do when your pond turns green? Let me know in the comments below.
Are you on Pinterest? I have boards dedicated to Garden Ponds and Pond Tips that you may find helpful.
Don’t forget to pin this post so you can come back to it later.