October 12, 2022 0 Comments

Often overlooked and rarely monitored as a water quality parameter, pH actually has a HUGE influence on the productivity of your fishery!

PH stands for Potential Hydrogen, generally most freshwater fish like a pH value of between 6.5 and 8. 

Limestone soil territories are often areas of hard water thanks to the alkaline soils that filter and calcify the water, so generally the source water in these areas is likely to be more alkaline. Naturally acidic water is generally found in areas of peat soil, identified by the growth of sphagnum moss which grows in acidic soils.

There are 3 key ways in which the pH has an influence over your fishery which we will go into a little more detail.

The impact of pH on the nitrogen cycle

Acidic water has a negative effect on the reproductive rate of aerobic bacteria. Nitrosomonas and Nitrobacter are the two aerobic bacteria that we need to convert Ammonia into Nitrite and then into Nitrate, so their presence is key to the organic digestion of waste materials in the water. If the reproductive rate of the bacteria is reduced, then this will have a knock on effect to the recycling of organic matter such as fish waste, leaf fall, silt and fish food.

Creating a healthy environment for the bacteria to thrive is going to make the organic breakdown process much more efficient and therefore quickly converting waste into forms of nitrate that seed a thriving food chain of plankton and the start of a fertile aquatic ecosystem.

The impact of pH on aquatic life

Acidic water dissolves trace metals in the water which become toxic to invertebrates and damaging to fish gills. Therefore, the diversity of the ecosystem and food chain is immediately compromised especially in areas where metal leaching occurs. The gill irritation can cause the cell wall of lamellae to thicken which will reduce the efficiency of oxygen diffusing into the blood, causing respiratory stress and poor fish performance. pH5.5 - 6.5 is harmful to fish and invertebrates where aluminium or mercury leaching occurs.

PH pulse

This term is given to the variation of pH in a 24 hour cycle related to the photosynthesis of weeds. The process of photosynthesis during the daylight hours absorbs carbon dioxide and produces oxygen, the respiration of the weeds at night absorb oxygen and produce carbon dioxide, when carbon dioxide mixes with water, you get carbonic acid. As the name suggests, carbonic acid will lower the pH during the night, until UV rays hit the weed and begin to photosynthesise to absorb that carbon dioxide and increase pH. This pH pattern over 24 hours is referred to as 'pH pulse'. As you can imagine the values will vary more in lakes with significant established weedbeds, and less of in impact in waterbodies with less weed.

What can you do to improve the pH value of your fishery?

Calcium carbonate applications will help to neutralise the pH of the substrate and water to create an environment more suitable for bacteria to thrive. However, you should take advice on whether this is the right option for your fishery, and only apply at the right time of year (ideally autumn/winter). The reason for caution is because you're creating a pH environment for bacteria to thrive, this will increase the oxygen demand and make more nitrates available which will feed weed/algae, another reason why Autumn/Winter applications are advised when bacterial activity is reduced and weed/algae are not thriving. 

Removing bankside trees will reduce the organic load when the leaves fall in the autumn. Paying special attention to the southern and western banks where trees block the most sunlight and contribute the most to the leaf fall from prevailing south westerly winds. By maximising the light and air exposure to the waterbody, you're killing 2 birds with one stone by optimising the natural organic digestion and full nitrogen cycle of your water whilst reducing the organic load from the leaf fall.

Watch our YouTube upload which explains all by clicking here.