pH is an important parameter to measure the acidity and alkalinity of water, and it plays a vital role in water quality management in aquaculture. In aquaculture, pH changes directly impact the growth and health of organisms in the water.

Continue reading. This article will introduce the impact of pH on aquaculture organisms and explain how to monitor and control pH.

What is pH in aquaculture?

The full name of pH is "potential of hydrogen." Aquaculture measures acidity and alkalinity based on the hydrogen ion concentration in water, creating a suitable living environment for aquatic organisms.

The pH value range is 0 to 14. At 25 °C, the hydrogen ion content in water exceeds 10-7 mol/L, and the corresponding pH value is higher than 7, indicating alkalinity; the hydrogen ion content is less than 10-7 mol/L, and the corresponding pH value is lower than 7, indicating acidity. If the pH value is exactly 7, it is neutral.

What do the different pH in aquaculture mean?

What Is Normal pH in Aquaculture?

pH is critical to the growth and health of aquatic organisms. Different aquatic organisms have different requirements for pH. Generally speaking, most fish and invertebrates grow best in water with a pH between 6.5 and 9. When the pH value of water is outside this range, the growth and cultivation of aquatic organisms may be adversely affected.

pH Range for Freshwater Aquaculture

The pH range for freshwater aquaculture is 6.5-8.0, which helps dissolve nutrients and minerals in the water and promotes the growth of aquatic plants, thereby providing food for some freshwater fish and forming a stable ecosystem.

Common Marine Organisms Ideal pH:

Corals: pH 8.1-8.4

Starfish: pH 7.5-8.5

Anemones: pH 7.8-8.4

Tropical fish: pH 7.8-8.4

Seahorses: pH 7.8-8.4

Oysters: pH 7.5-8.5

Seaweed: pH 7.8-8.4

What Are the Effects of pH on Aquaculture?

Water bodies are very important in aquaculture, and pH is an important indicator of water quality, which will directly affect changes in water quality, such as the vitality of algae and the presence of carbon dioxide. The effects of pH on aquatic animals mainly include the following aspects:

Affecting the Health of Aquatic Animals:

The pH value directly affects the acid-base balance of the blood of farmed animals. A pH value that is too low can cause blood poisoning in farmed animals. Acidosis can affect the functions of various enzymes and hemoglobin in fish, obstruct blood circulation, and reduce oxygen-carrying capacity.

Even without oxygen, acidic water can still reduce the floating heads of fish, shrimps, and crabs, increase toxicity, lead to respiratory obstruction, reduce oxygen consumption, and sharply reduce metabolism, affecting the growth rate of aquatic animals.

Affecting the Survival of Aquatic Organisms:

In acidic water bodies, the solubility of phosphates will be affected, microbial reproduction will be inhibited, and the material metabolism of the water body will slow down, thereby affecting the growth rate.

Too high a pH value will affect the activity of microorganisms and their ability to degrade organic matter, affecting the unassisted reabsorption and utilization in the water body, thus wasting food. When the pH value is 4--5, it may cause pond overturning of aquatic organisms.

Impact on the Quality of the Water Environment:

The pH value has a great impact on the physicochemical properties of aquaculture water. When the pH value is low, it may increase the toxic effect of iron ions. When the pH value is high, protein corruption, increased ammonia ions, increased alkalinity, etc., may occur, leading to the photosynthesis of plankton, affecting the concentration of organic matter in the water, and affecting the growth and reproduction of fish.

Aquaculture Water pH Monitoring Methods

1. pH test strips: Quickly dip the test strip into the water sample, wait for 10 seconds, remove it, wait 15 seconds to 1 minute, observe the color change of the test strip, then compare it with the control card and record the pH value.

Note: Avoid touching the test area when handling the pH test strip.

2. Digital pH meter: Check the condition of the equipment, make sure the probe is not damaged, and calibrate the pH meter. Next, put the water sample into a clean container, immerse the pH sensor probe completely in the liquid to be tested, wait for the pH sensor to display stable data and record it, and finally remove the probe.

Note: Be sure to clean the pH meter probe with deionized or distilled water before measuring, and wipe it clean.

3. Colorimetric pH test kit (test tube, reagent, colorimetric card, etc.): Place the water sample into the test tube, add the specified amount of reagent, cover the lid and shake gently, then wait for the water sample to change color for a few minutes, and record the pH value against the colorimetric card.

Note: Avoid contamination of the kit and water sample before testing, and ensure that the test tube and the comparison card are under the same light source to reduce pH errors.

Aquaculture Water pH Monitoring Applications

Monitoring the pH value of water bodies is one of the key tasks of aquaculture. By regularly testing the pH value of water bodies, acidity and alkalinity problems in water bodies can be discovered and dealt with on time.

Generally speaking, pH value can be measured using a portable multi-parameter water quality meter, and the instrument needs to be calibrated before measurement.