Better clarification about pH and Alkalinity in shrimp pond. Water quality series -3
Hello everyone:
Most of us confused between pH and alkalinity in the pond ecosystem. If there is low concentration of pH and alkalinity means we can increase but if there is high pH and alkalinity means it is some difficult to reduce.
pH and Alkalinity are related but different.
pH and Alkalinity:
If you have shrimp pond then you definitely know the variance of pH in the water. You want to know means , you can check 4 to 5 times in a day. you must saw the pH fluctuations. Yes, pH is very important factor determines the shrimp culture. based on the level of pH you can tell , what happening in your shrimp pond.
Fluctuations of pH is mainly determined by amount of carbon dioxide in your pond water. Other factors like soil pH, soil deposits like calcium carbonate, planktons density also determines the changes of pH in your water.
pH :
I am also tell the same meaning, pH is determined by hydrogen ion concentration.
pH low - high hydrogen ion concentration.
pH high - high hydroxide ion concentration.
You can note in your pond.....
Morning - low pH
Afternoon - high pH.
Night time - again low pH.
Reason for this.......
The main reason is the presence of carbon dioxide in your pond water. Yes, in night time, all organism in your pond started respiration( shrimp, planktons, microorganisms). They releases excess carbon dioxide in your pond...
Night time - organism release - more co2 ..
When they releases more carbon dioxide, there is an increasing concentration of co2 in your water. In water, the co2 is first reacts with water and forms weak acid called carbonic acid..
Excess CO2 + water H2O gives carbonic acid H2CO3
When this acid formed then it will reduce your pond pH . It happens in every pond and also various weak acids produced from decomposition of organic matter.
(Don't think - I told carbon dioxide in water increases in night time, anyway this increased carbon dioxide does not affect the oxygen that present in your pond)
This the reason why pH decrease at night time.
Important factor you must remind:
Yes, this carbon dioxide in your pond water not only comes from animals respiration and also comes from atmosphere. This the reason given by Henry's law.
This law states the equilibrium of gases at certain Temperature and pressure. It determines the solubility of gases.
Example.......
If your Pond water have low CO2, at the same time Atmosphere contains - high CO2. In this, the carbon dioxide is diffused into your pond to reach the equilibrium. It is diffused from high concentration to low concentration. It is also one of the reasons of increasing carbon dioxide into your pond water..
Why aeration important?
If you aerate your pond continuously, then the carbon dioxide present in your pond leaves out of your water, then it reduces the chance for decreasing pH of your water. All are happening like the same process, they moves from one concentration to another like this....
Why pH high in afternoon?
In afternoon time, there is no free carbon dioxide available at your pond. At certain pH of 8.3 there is no carbon dioxide is present and there is no chance for formation of carbonic acid in your pond...... So, in afternoon , planktons start photosynthesis, in this process it absorbs all carbon dioxide that present in your water....
Important:
Imagine that, planktons in your pond is doing photosynthesis at sunny time.. if no carbon dioxide available for its photosynthesis, then it will take carbon dioxide from bicarbonate which is present in the water..... By this reaction , planktons take CO2 from bicarbonate and gives one carbonate ion and hydroxide ion, it causes increases in pH. If your pond have high bloom, then you can tell ,your pond have high pH at afternoon and many times......
Are you get bored? Ok no problem it is very interesting to read the relation between pH and alkalinity...... Continue reading for Better clarification......
Other ways of increasing pH :
Other ways include any chemical application in your pond water increases pH of the water. Example: lime application.
Alkalinity:
Alkalinity in the water determines the acid resistance. Yes, molecules in the alkalinity bases takes hydrogen ion from acid. This is called buffering. This is the reaction, how base neutralize acid especially occurs in ponds.
Very important in pond water. It is a base which mainly contains carbonates, bicarbonates , phosphates and other bases. It determines the capacity of your water to fight or resist against pH in your pond.
Already I told..... At night time, there is decrease in pH. If your pond have low alkalinity then, it can't resist the acid in your pond. If your pond have good Alkalinity, it can buffers the low pH in your pond especially at night times...
In your pond , there is a series of reaction occurs. That means reversible reactions.... So the Alkalinity, pH are varies from time to time in your pond ecosystem.
CO2 + H2O - H2CO3 then the H+ ion in this acid is taken by bicarbonate in the system. It increases the pH then the excess H+ ions in the bicarbonate is taken by carbonates and pH increases and neutralize. likewise happens in water.
From low pH to high pH :
CO2 + H2O - H2CO3 then the hydrogen ion picks by bicarbonate H+ and HCO3 and gives CO3 and H..
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| This is the system of alkalinity and pH in water. |
This reaction occurs in both way. If your pond have pH of 6 then it refers the low level of buffering in your pond.
Water and carbon dioxide forms
Carbonic acid (weak acid)
Bicarbonates neutralize the acid by taking H+from this acid....
pH increases in your water...
If having very high alkalinity then, the system changed to carbonates...
Based on the carbon dioxide concentration, this reaction will changes...
Example: In night time how alkalinity buffers pH. In night time pH is going down, at that time carbonates takes the H + ions in the water. At that time when carbonates is not available in your water , then these H+ ions will taken by bicarbonates and buffers the acid. Excess hydrogen ion reacts with bicarbonate and forms weak acid called carbonic acid.. this acid breaks to CO 2 and water then the CO 2 moves out from water(in morning time). This is the series of reaction occurs.
Remind one thing...
If your pond have high pH then don't add minerals. Because at high pH only carbonates ions are available. If we applied minerals like calcium then it reacts with carbonates and precipitated. After some time, it will releases into water . Calcium carbonate formation is the main source of Alkalinity in water. So only we mentioned in alkalinity value as mgCaco3. At high pH lime also not working.
Temperature also causes the variation. High temperature causes high dissociation of H+ ions in water....cooler water can hold more carbon dioxide and causes reducing pH of pond.
See the graph, this is circulated in the water. It is reversible reaction. They are unstable and changed from one phase to another. At low pH , no carbonates ions available.
I hope now you slightly understood about these. Read two to three times then you will be clear in this...see graph....
Thank you 😊.
P.Dhivagar BFSc,
Technical executive - Growel feeds.
9384346193
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