How to Treat and Prevent a pH Problem

Whether you are stocking your pond with Goldfish, Koi or Wildlife, controlling the pH of your pond is critical. These may fluctuate naturally, but otherwise they should remain consistent in a healthy pond.

pH is a scientific scale which measures the acidity or alkalinity of a liquid. The ideal pH of a fishpond should be as close to 7 as possible; though a pH between 6.5 and 7.5 is ok. These are measured as seen below:
• An acidic environment is where the pH is less than 7.
• An alkaline environment is where the pH is greater than 7.

If your pond has a pH level of below 4 or higher than 11, there is a serious issue and this requires urgent treatment. 

The common signs of a pond pH crash are not visible, but often include the following:
• Sudden death of fish or wildlife.
• Fish resting at the bottom of the pond.
• Fish gasping for air at the surface.
• Excess algae blooms.
• Lethargic fish.
• Damaged pond plants.
• Changes in water clarity.
• Pond Odour.

These symptoms may be related to another problem your pond experiencing, but running a test immediately will help to rule out certain problems.

If you experience any of the above symptoms, you should test your pond straight away. This can be done with either the Tetra 6 in 1 Test Kit or the Blagdon Pond Health Test Kit. You may even want to purchase a Digital pH Tester if your pond has regular pH fluctuations. A local garden centre may also have a water testing service, which can measure the pH of your pond along with various chemicals as well.

Why are pH fluctuations dangerous?

pH fluctuations, or a pH crash, is when a pond experiences a sudden change in the pH level; normally it is when the pH goes below 6.5 or higher than 7.5. The pH should be monitored monthly to prevent a pH crash as they can cause significant damage to the biological balance of the pond. A pond undergoing a pH crash can also be difficult to keep clean and healthy, due to the damage done to the pond balance.

What causes and increases the chance of pH fluctuations?

The pH in your pond can be affected by many things; however, the main issue is normally unstable water. The ‘stability’ of the pond’s pH is determined by the carbon hardness (KH) of your pond; this determines how the ponds pH fluctuates. If the KH levels are lower, you have a higher risk of a pH crash because the water is more susceptible to bigger pH changes in a shorter space of time.

Further to this, smaller ponds may have a higher chance of pH fluctuations, because sudden changes will affect the whole body of water quicker than a larger pond. You can use our Pond Calculator to calculate the volume of water in your pond.

If the pond’s location experiences heavy rainfall, this can also cause pH fluctuations because rainwater is slightly acidic (measuring a pH of around 5.6).

How to treat pH fluctuations

The best way to treat and prevent a pond pH crash is to use either the Blagdon pH Adjuster for Alkaline Ponds or the Blagdon pH Adjuster for Acid Ponds. These should be used with a pH testing kit (either the Tetra test kit or the Blagdon test kit) and the pond should be monitored regularly after treatment; just in case you need to treat the pond again.

You may also want to run a partial water change on your pond; this means removing up to 25% of the pond water and replacing this with either rainwater or tap water. This should help to rebalance the pond; though please make sure your pond is dechlorinated with a Chlorine remover treatment.

You may also find the below blogs useful:
• Common Pond Discolouration Problems
• Signs of Low Oxygen in Ponds
• Water Quality

If you have any queries, please email us on info@pondkeeper.co.uk.