Blog Article

Controlling pond algae

Controlling pond algae

Date: 12 June 2023 | By: aqua

If recently you’ve noticed green film on the surface of your pond or a green hue to the water then it’s probably due to a build up of algae, likely caused by the warm weather and high levels of sunshine. However, controlling algae in your pond may or may not be something you feel is necessary, and it could disappear by itself as Autumn arrives.

Bear in mind that if you have a wildlife pond it’s best not to disturb the ecosystem by removing the algae, in such an environment it will provide vital shelter and hiding places for your ponds inhabitants.

Not only is algae unattractive, it also reduces oxygen levels, which can be hazardous for aquatic life. Here's our advice and suggestions on controlling your pond algae.

removing algae and sludge during pond maintenance

Reasons for algae in your pond…

  1. An increase in the amount of sun – if your pond is in a very sunny spot without much planting to offer shade to the waters surface, then the water can turn green.
  2. A build up of pond debris – such as fish faeces, fallen leaves and invasive pond weed can be a factor.
  3. High levels of nutrients in the water – this could be due to a large amount of sludge at the bottom of the pond, fertiliser run off from the lawn or using the hose to top up the water level.

Filling pond with water from hose

Did you know? It’s the phosphates in tap water that when used to top up your pond can cause it to turn green. Where possible use rainwater to top up and consider installing a rainwater harvesting tank, if space allows, to utilise when rain levels are lower in summer. If you must use the hose to top up your pond you could consider getting a filter fitted to the tap, to limit the amount of phosphates entering the pond.

Controlling algae in your pond - how to remove a build up…

There are a few things you can do to remove the algae from you pond, but one thing not to do is change the water, as this will only offer a short term fix, and it can be detrimental to the health of aquatic life.

The best solution is to look at the conditions of your pond to see which you can remedy. Some ideas are:

  • installing a net to catch fallen debris in Autumn
  • introducing large potted shrubs close to the waters edge or water lilies in the pond itself to provide shade to the water’s surface
  • minimising the use of garden fertilisers
  • rehoming fish to limit the build-up of faeces if pond is overstocked

Algae in pond waterfall

Ways to discourage algae from returning to your pond…

  • Floating a bale of barley straw in a mesh bag (50g per square metre) in the pond will discourage algae and one bale can last up to 6 months. Replenish once the straw has turned black.
  • Adding a UV pond filter will constantly remove algae and debris from the water.
  • Adding a fountain to aerate the water will help to reduce certain types of algae, but not all.
  • If you’re considering installing a new pond, then two key considerations to limit algae would be to site it in partial shade, and to have a depth of at least 70cm, to stop it warming up too quickly in the summer months.

You can of course always call on Broadley Aquatics to carry out a pond clean, install a UV filter and offer advice on pond care.

Pond Clean Algae BEFORE AFTER


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