Understanding water pH
In its most basic terms, pH is the way of indicating whether an area of water is acid, alkaline or neutral.
pH is measured on a scale of 1 to 14: 1 is pure acid, 14 is pure alkaline and 7 is neutral.
Managing pH levels is vitally important to success in fishkeeping as fish must have a healthy and balanced environment to survive. A safe aquarium pH varies from fish to fish, but is typically between 6.5 to 8.5.
How does pH affect water?
To better understand pH, we need to delve further into the chemistry of water. We all know that water’s chemical description is H2O. This is a mix of free positively charged hydrogen ions (H+) and negatively charged hydroxyl ions (OH-). It is the varying proportions of these ions that causes the differences in water pH. If there are more OH- ions then water will be more alkaline. But if there are more H+ ions then the water will be more acidic.
pH can be affected without you realising. All it takes is for new minerals to be added to the water. They will release ions which will contribute to the dominance of either the OH- or H+ ions in the water. These new minerals may be added to the water through rocks or wood used as décor, carbon dioxide from respiration or from decaying food or plants.
Is high pH water bad for fish?
High or low pH can cause unexplained fish death, irritability in your fish, gasping at the surface and changes in colouration amongst other issues.
Like many other water quality issues, changes in pH in your aquarium are invisible and unless you test your water regularly you will only notice the issue when things start to go wrong.
Did you know that for every increase of one pH, there is a 10-fold change in the concentration of hydrogen ions?
For instance, a pH of 6 is 10x more acidic than a pH of 7, and a pH of 5 is 100x more acidic than a pH of 7! As you’ll see, even a ‘small’ change in pH has a big impact on the water in which your fish live, so regular pH testing is crucial to happy and healthy fish.
pH lowering products often claim to contain a “buffer”. Simply put, a buffer is a way of using chemicals to prevent pH falling to a dangerous level. The chemicals will prevent the dominance of H+ ions and help a stable pH.
Buffers can be added by the use of certain products, but they may be naturally present in tap water. Hard water contains minerals, and these minerals are the natural buffers that help stabilise the pH in your water. Soft water does not contain these mineral buffers, so if you live in a soft water area you may experience more issues with a fluctuating pH.
To better understand pH, we need to delve further into the chemistry of water. We all know that water’s chemical description is H2O. This is a mix of free positively charged hydrogen ions (H+) and negatively charged hydroxyl ions (OH-). It is the varying proportions of these ions that causes the differences in water pH. If there are more OH- ions then water will be more alkaline. But if there are more H+ ions then the water will be more acidic.
pH can be affected without you realising. All it takes is for new minerals to be added to the water. They will release ions which will contribute to the dominance of either the OH- or H+ ions in the water. These new minerals may be added to the water through rocks or wood used as décor, carbon dioxide from respiration or from decaying food or plants.
Did you know that for every increase of one pH, there is a 10-fold change in the concentration of hydrogen ions?
For instance, a pH of 6 is 10x more acidic than a pH of 7, and a pH of 5 is 100x more acidic than a pH of 7! As you’ll see, even a ‘small’ change in pH has a big impact on the water in which your fish live, so regular pH testing is crucial to happy and healthy fish.
pH lowering products often claim to contain a “buffer”. Simply put, a buffer is a way of using chemicals to prevent pH falling to a dangerous level. The chemicals will prevent the dominance of H+ ions and help a stable pH. Buffers can be added by the use of certain products, but they may be naturally present in tap water. Hard water contains minerals, and these minerals are the natural buffers that help stabilise the pH in your water. Soft water does not contain these mineral buffers, so if you live in a soft water area you may experience more issues with a fluctuating pH.
How does pH affect aquarium fish?
Fish have also learnt to adapt to changes in pH. Before you decide what fish you want in your aquarium it is worth considering the type of water you have and the natural pH.
Depending on their origins fish have become used to certain surroundings which generally include varying combinations of temperature, water hardness and pH. If you have naturally acidic, soft water you are going to have to work more to keep fish that prefer harder, more alkaline water so it is important to speak to your aquatic retailer before taking certain fish on.
What is a good pH for my fish tank?
The ideal pH for your fish tank depends on the type of fish you are keeping. Generally speaking, most fish thrive in water with a pH between 6.5 and 8.5, although some species have specific requirements outside of this range.
Fish that require acidic conditions such as discus and tetras, do best in slightly lower pH levels between 6.0 and 7.5. While salt water fish and livebearers are more comfortable in slightly higher pH levels around 8.0.
What causes high pH in fish tanks?
High pH levels in an aquarium can be caused by a number of different factors. The most common causes are overfeeding, decaying organic matter, high levels of calcium carbonate (CaCO3), and high levels of alkaline salts such as sodium bicarbonate.
Overfeeding can lead to the production of too much waste which can result in an increase in ammonia, nitrite and nitrate levels. All of these compounds can cause a spike in pH, as well as potentially harming or killing your fish.
Decaying organic matter such as uneaten food or dead plant material can also release ammonia and other compounds into the water, resulting in an increase in pH levels.
Symptoms of low pH in fish tank
When the pH in a fish tank is low (acidic), it can have negative impacts on the health and well-being of the fish.
- Fish Stress
- Sluggishness or Lethargy
- Low appetite
- Damaged Fins and Tissue
- Abnormal Behavior
- Poor Growth and Development
- Reproductive Issues
Symptoms of high pH in fish tank
When the pH in a fish tank becomes too high (alkaline), it can have adverse effects on the health and well-being of the fish.
- Fish Stress
- Reduced Oxygen Levels
- Altered Water Chemistry
- Poor Digestion and Nutrient Absorption
- Damaged Gills and Tissue:
- Lethargy and Reduced Activity
- Abnormal Behavior
Fish have also learnt to adapt to changes in pH. Before you decide what fish you want in your aquarium it is worth considering the type of water you have and the natural pH.
Depending on their origins fish have become used to certain surroundings which generally include varying combinations of temperature, water hardness and pH. If you have naturally acidic, soft water you are going to have to work more to keep fish that prefer harder, more alkaline water so it is important to speak to your aquatic retailer before taking certain fish on.
How to conduct a pH test
Testing the pH is easy and inexpensive. There are test kits available that allow you to test your water quickly and accurately.
To perform a test, all you need to do is follow the manufacturer’s instructions. This usually involves taking a sample of aquarium water and adding a few drops of the testing liquid or powder from the kit. The resulting colour will indicate the pH and can be compared to the colour chart provided.
Once you’ve determined what the pH is, you can then decide whether it needs to be adjusted or not. If it does need to be changed, there are several products available that can help raise or lower the pH as required.
