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Water Quality Analysis

pH

1. What is pH?

pH is the measure of hydrogen ion concentration.
The optimum water pH range in the shrimp pond is 7.5-8.5. It is essential to stabilize the pH with in this range.
The pH value in the water is normally lowest in the early morning and highest in the afternoon.
For the best water quality, the maximum diurnal pH fluctuation should not exceed 0.5. If pH changes significantly, it can make shrimp shocked, weakened and stop eating.
It is important to maintain a stable pH at a safe range because it affects the metabolism and other physiological processes of culture organisms.
If high or low pH extends for a long time, it will make shrimp grow slowly, stunting and susceptible to diseases

2. Why pH is considered as most important factor in shrimp culture?

pH is an important parameter to control the growth and survival of shrimps. pH is vital environmental characteristics and it also affects the metabolisms and other physical process used to reduce soil acidity.

3. What are all the factors affect the pH?

The pH will vary in pond environment depending on a number of factors

Acid sulfate soil and acidic source of water
Poorly buffered water
Rate of rainfalls in pond areas
Stocking density of shrimps
Feeding & rate of sludge formation in pond bottom.
Presence of micro/ macro organisms
Existence of phytoplankton in pond water. Rate of carbon dioxide production in pond water
Quantity of respire by aquatic species in the pond water.

4. Why the pH is rising during the day and decreasing at night?

The pH in ponds will rise during the day as phytoplankton and other aquatic plants consume CO2 from the water during photosynthesis.
As the sun begins to set in late afternoon, photosynthesis decreases and eventually stops, so pH falls throughout the night as respiring organisms add carbon dioxide to the water. When the sun rises, plants resume photosynthesis and remove carbon dioxide from water, causing pH to rise again. The daily interplay of respiration and photosynthesis

5. If pH level is low means what will be happened to shrimps?

The low pH levels will cause the shell of shrimp to become soft. This is due to the shell of the shrimp being composed of calcium carbonate which reacts with acid.

6. If pH level is high means what will be happened to shrimps?

High pH may also increase the toxicity of other substances. For example, the toxicity of ammonia is ten times more severe at a pH of 8 than it is at pH 7. It is directly toxic to aquatic life when it appears in alkaline conditions.

7. What is the adverse effects on shrimps due to Sub-optimal pH?

If pH changes significantly, it can make shrimp shocked, weakened and stop eating.
In high or low pH extends for a long time, it will make shrimp grow slowly, stunting growth and susceptible to diseases.
It can cause stress, less survivals, low production and leads to poor growth.
Signs of sub optimal pH includes increase mucus on the gill surfaces, black gill disease, damage to the eye lens, abnormal swimming behavior, loose shell, soft shell, irregularity in molt, poor phytoplankton and zooplankton growth.

What is the indicator of fast changes in pH?

Fast changes in pH can also be an indicator of a full algae crash, meaning the population of algae in the pond dies, both lowering the pH dramatically, and more critically, absorbing much of the excess dissolved oxygen in the process.
A reduction in pH from 8.2 to 6.5 or an increase to 10.1 during L. vannamei rearing made the shrimp more susceptible to Vibrio alginolyticus compared to those raised at a pH 8.2.

9.How to avoid the daily fluctuation in pH?

It can be minimized by using fertilization and feeding rates that do not result in excessive phytoplankton, liming low alkalinity ponds, and applying a soluble calcium source such as gypsum (calcium sulfate) to ponds with moderate to high alkalinity but low calcium concentration.

Salinity

1.What is Salinity?

Salinity is the total concentration of dissolved ions in 1 litre of water and is expressed as parts per thousand (ppt).
Salinity as a single factor plays an important role in shrimp farming as it is responsible for many functions such as metabolism, growth, osmotic behaviour, reproduction etc.
Salinity is considered the most important abiotic factor affecting the growth and survival of penaeid shrimp.
The wide range of salinity tolerance of shrimp from 0.5 to 45 ppt

2. Why should test Salinity in shrimp ponds?

To know the mineral availability of pond water

3. Why salinity is important in shrimp ponds?

Salinity plays an important role in the growth of shrimps through osmoregulations of body minerals from that of the surrounding water.
For better survival and growth optimum range of salinity should be maintained in the aquaculture ponds.

4.Why should maintain optimal salinity in shrimp ponds?

Optimal salinity is required for shrimp to establish the metabolic processes properly.
If the salinity in the shrimp body fluids is higher than the environment, the water in the environment will enter into the shrimp body so that the cell will swell.
On the contrary, if the environmental salinity is higher than the salinity of shrimp body fluids, the water in the shrimp body will come out so that the shrimp become thin.
When shrimp is exposed to salinity, higher or lower than its optimum requirement and hence more energy is used for osmoregulation and hence more feed is required to obtain optimum growth.
Molting is extremely high or low salinities may require more time and energy in normalizing hemolymph osmolality. So, we have to maintain optimal salinity in shrimp ponds.

5. If salinity is beyond the optimal means what will be happened?

If the salinity is allowed to go beyond the optimal limit, the shrimp refrain from taking normal food and hence are emaciated and become susceptible to disease.
Poor growth due to poor molting cycle.

6. If salinity is high or low in shrimp pond means what will do immediately?

When extreme high salinity, it is necessary to make pond deep water exchange, decreasing pond water levels and retrieving with water from the reservoir channel if its salinity is lower.

Alkalinity

1. What is alkalinity and Total alkalinity?

Alkalinity is the capacity of water to neutralize acids without an increase in pH. This parameter is a measure of the bases, bicarbonates (HCO3-), carbonates (CO3--) and, in rare instances, hydroxide (OH-).
Total alkalinity indicates the quantity of base present in water --bicarbonates, carbonates, phosphates, hydroxides, etc.
The most important components of alkalinity are carbonates and bicarbonates.
The desired total alkalinity level for vannamei lies between 100-160 mg/L CaCO3, but no less than 80 mg/L.
When water alkalinity is low, broad pH variations occur resulting in shrimp stress, reduced growth, and even mortality.
Water alkalinity for whiteleg shrimp farming:

Newly released shrimp: 100 - 120ppm
N45 days or older shrimp: 120 - 150ppm
N90 days or older shrimp: 150-200 ppm

2. Why alkalinity is more important in shrimp ponds?

Alkalinity plays a major role in shrimp culture ponds because of its involvement in the shrimp molting process.

3. If alkalinity is low in shrimp pond what will be happened?

Low Alkalinity leads to broad pH variations which result in reduced growth and even mortality in shrimp.

4. If alkalinity is high in shrimp pond what will be happened?

High alkalinity levels may stop the process of shrimp molting due to excess salt loss.
Excess alkalinity may be harmful to Shrimp Growth and Survival.

5. If alkalinity concentrations are below the suggested level means what will do?

It can be increased by adding agricultural limestone [CaCO3 and CaMg(CO3)2]. Agricultural limestone will not increase pH beyond a maximum of 8.3. The use of hydrated lime (CaOH2) or quick lime (CaO) is not recommended because either of these compounds can cause the pH to rise very rapidly, to levels that are harmful to aquatic life.

6. If alkalinity concentrations are high the suggested level means what will do?

The application of calcium carbonate can also aid to decrease alkalinity since it is a source of calcium. This treatment will tend to decrease potentially high pH levels during photosynthesis, since increased calcium ion concentrations will result in the precipitation of both calcium carbonate and inorganic phosphorus. Both events cause decreased pH.

Hardness

1. What is hardness?

Hardness is the measurement of all divalent cations (i.e., those ions carrying a plus two charge) of which calcium and magnesium (Ca++, Mg++) are the predominant species in water and is expressed in milligrams per litre of equivalent of calcium carbonate.
The calcium and magnesium levels in water are very essential element for L vannamei. The magnesium concentration must be at least three times than the calcium concentrations.
These calcium and magnesium ions may be absorbed by shrimp through their gills and thus are important not only in water quality but in the nutrition of the animal.
The hardness is a vital factor in maintaining good pond equilibrium.
Hardness is depending on salinity of Water(generally 1ppt is approx,.200 harness)

2. Why to test the hardness of water?

To know about the mineral composition of the water.

3. What are the importance of calcium and magnesium in shrimp farming?

Minerals have many physiological functions to maintain acid–base balance and are important in osmoregulation. Among major minerals, Calcium (Ca) and magnesium (Mg) are considered to be very important for molting and new shell formation.

4. Relationship between Hardness and alkalinity?

Hardness and alkalinity are more important for the exo-skeleton of shrimp. Hardness is often confused with alkalinity because both are expressed in similar terms (mg/L as CaCO3) and often hardness and alkalinity values are similar. However, if the alkalinity is from sodium carbonate instead of calcium or magnesium carbonates it is possible to have low hardness and high alkalinity. High hardness and low alkalinity may occur in acidic well or surface waters.

5. How calcium and magnesium influence the growth of shrimps?

Calcium is essential and major component of shell
Calcium is a major cation essential for shrimp farming as the crustacean exoskeleton development requires calcium to be sequestered from the medium and feed.
Calcium is also important in the molting process of shrimp, and can affect the hardening of the newly formed shell.
Calcium along with magnesium also contributes to the hardness of the water and calcium ions prevent large diurnal variations in the water pH due to plankton dynamics as they react with bicarbonate ions HCO3- forming calcium carbonate, CaCO3.
Magnesium is an important cation required for osmoregulation in shrimps. Magnesium is the second most important ion after potassium which needs to be supplemented so as to make the water suitable for shrimp farming.

6. If hardness is low means what will be happened?

Low hardness water contains insufficient calcium ions for protection of shrimp against acidity and metal toxicity, calcium is also very essential for shrimps.

7. How to increase the hardness value?

Low hardness can be increased with agricultural limestone (calcium carbonate), agricultural gypsum (calcium sulfate), or food grade calcium or magnesium chloride.
Magnesium concentrations in such waters can be increased by the application of potassium magnesium sulfate. Magnesium sulfate (Epsom salt) also is a soluble source of magnesium.
There are some pond waters in which the alkalinity is high and calcium concentration is low. This combination can lead to dangerously high afternoon pH when photosynthesis is proceeding rapidly. Calcium sulfate can be applied to increase the concentration of calcium ion.

Ammonia & Nitrite

1.Ammonia & Nitrite

Ammonia is continuously produced by shrimps as normal excretion
In all water quality parameters which affect shrimp Ammonia is most important after Oxygen in intensive and semi intensive systems
Excess Ammonia causes stress and gill damage to the shrimps
Ammonia in water converts in to Nitrite by Nitrifying Bacteria
Nitrite is also Toxic, the effect we can see it on feed intake and growth of the animals only
The Toxic ammonia (Un ionized Ammonia – NH3) can be calculated from the Total ammonia from the following table.

pH	Temperature ˚C
	24	26	28	30	32
7.0	.0052	.0060	.0069	.0080	.0093
7.2	.0052	.0083	.0110	.0126	.0150
7.4	.0131	.0150	.0173	.0198	.0236
7.6	.0206	.0236	.0271	.0310	.0369
7.8	.0322	.0370	.0423	.0482	.0572
8.0	.0502	.0574	.0654	.0743	.0877
8.2	.0772	.0880	.0998	.1129	.1322
8.4	.1171	.1326	.1495	.1678	.1948
8.6	.1737	.1950	.2178	.2422	.2768
8.8	.2500	.2774	.3062	.3362	.3776
9.0	.3456	.3783	.4116	.4453	.4902

2. Influence of Pond Parameters on Ammonia & Nitrite

An Increase in Temperature thus pH leads to Ammonia Toxicity
Low Salinity areas are more prone to Ammonia toxicity compare to high salinity areas
A decrease in DO leads to Ammonia Toxicity
Young individuals are more susceptible to Ammonia Toxic Effect.
Low pH leads to High Nitrite Toxicity
Low Salinity areas are more prone to Ammonia toxicity compare to high salinity areas
Higher the Hardness lower the Nitrite Toxicity

3. Why should we care for Ammonia & Nitrite?

Shrimps exposed to low levels of Ammonia for longer period are more susceptible to Bacterial infections
In high concentrations of Ammonia mortality starts
Decrease the feed intake cause poor growth
High levels of Nitrite compete with oxygen, binds in haemolymph, so oxygen will not be available for normal activities of the shrimps
Nitrite will irritate the body surface and gills
Decrease feed intake, leads to very slow growth
Cause Running Mortality Syndrome which gives less survival

4. How does Ammonia & Nitrite increase in Pond?

More than 60% of the total ammonia is excreted by shrimps directly and this will continue throughout the culture days
The decomposition of the solid wastes such as excess feed (uneaten feed) and faeces leads to ammonia production
The Nitrifying bacteria which is normally present in the water converts ammonia into Nitrite
As ammonia production is a continuous process by shrimps in culture the excess ammonia is continuously converted to nitrite, so the levels of nitrite is increasing constantly
The Conversion of the nitrite into Nitrate is normally requires nitrite reducing/consuming bacteria which is usually slow growing bacteria and not naturally present in pond water

5. How to observe the changes of ammonia and nitrite in pond/Animal performance?

Water – Lab Testing
Animal – Not much significant observation
Feed intake – Less feed intake
Water - Lab Testing
Animal – Lethargic, Brown/black gill, Half/empty gut, Slow/no growth
Feed intake – Less feed intake/no feed intake

6. What is the safe and unsafe levels of Ammonia and Nitrite?

	Safe Level	Unsafe Level
Total Ammonia (TAN)	< 0.5 ppm	>1.0 ppm
Toxic Ammonia (NH3)	< 0.01 ppm	>0.05 ppm
Nitrite (NO2-)	< 0.1 ppm	>0.1 ppm

7. What are the other parameters influence on Ammonia and Nitrite?

An increase in pH leads to increased ammonia toxicity
An increase in temperature leads to increased ammonia and nitrite toxicity
A decrease in salinity leads to increased ammonia and nitrite toxicity for most shrimp species
A decrease in DO leads to increased ammonia and nitrite toxicity
Younger individuals are more susceptible to toxic effects
A decrease in salinity ammonia becomes more toxic
Higher the temperature higher the toxicity
Higher the salinity lower the toxicity
Higher the hardness lower the toxicity
Lower the pH higher the toxicity

8.How to monitor pond for changes in Ammonia and Nitrite?

Through frequent testing of pond water in lab

9.How to interpret the lab results?

	Optimum Level	Tolerant Level	Toxic Level
Total Ammonia (TAN)	< 0.5 ppm	0.5 – 1.0 ppm	>1.0 ppm
Toxic Ammonia (NH3)	< 0.03 ppm	0.03 – 0.05 ppm	>0.05 ppm
Nitrite (NO2-)	< 0.1 ppm	0.1 – 1.0 ppm	>1.0 ppm

10. What is the Nitrate and its relationship with Ammonia and Nitrite?

Nitrate is a non-toxic form of nitrogen, the main source of nitrogen for algae and other plants.
In Nitrogen cycle more toxic Ammonia is converted in to less toxic form nitrite and further converted to non-toxic form Nitrate which is bio available form of Nitrogen.
Nitrite utilising bacteria converts nitrite in to nitrate and it can’t be absorbed by shrimps directly, so it is non-toxic to shrimps.

11. How to overcome the Ammonia and Nitrite problem?

B Yuka 30 directly reacts with ammonia and decrease the levels, so this can be used at high levels of Ammonia for immediate effect.
Yuka – The probiotic in Yuka utilizes ammonia and converts in to Nitrite, so the toxic ammonia produced continuously by shrimps is converted to less toxic Nitrite. The Nitrite reducing Bacteria in Yuka converts Nitrite in to Nitrate, so the Nitrite level is maintained at below toxic limits

12. How frequently we have to use Yuka?

Yuka: 1L/acre for every 15 days.
B Yuka 30: 500g/Acre along with Yuka: 1L/acre
3rd day again Yuka 1L/acre as booster dose
Continue Yuka as per the preventive schedule and follow other farm BMPs

13. Why to monitor Ammonia and Nitrite even in good time?

As ammonia & Nitrite production is fast and continuous process the accumulation of Nitrite is normal one, but nitrite will lead to less feed intake & poor growth. This toxic nitrite should be converted in to Nitrate so that the stress is relieved for shrimps, resulted in increased feed intake thus growth.
Whenever the Nitrite level is maintained below the toxic limit, shrimp growth will be good. To maintain the nitrite & ammonia levels below the toxic limit, we have to test and monitor the levels in pond water.

Vibrio

1. Bacterial infections:

The bacteria causing diseases of penaeid shrimp constitute part of the natural microbial flora of seawater.
Accumulation of un-utilized feed and metabolites of shrimp in the culture tanks and ponds enrich the water with organic matter that supports the growth and multiplication of bacteria and other microorganisms.
Bacterial infections of shrimp are primarily stress related. The most common shrimp pathogenic bacteria belong to the genus Vibrio.

2. What is vibriosis?

Vibriosis is an infectious disease caused by gram-negative bacteria in the family Vibrionaceae.
The acute infection usually occurs when shrimps are one month old. Therefore, sometimes the farmers call it as one-month mortality syndrome.
In higher salinity areas, the severity of this problem is usually greater and is caused by luminous species of bacteria. In this case the farmer may call the problem luminescent vibriosis. The clinical sign is not obvious.

3. Why to test vibrio in pond water?

To know the pathogenic bacteria vibrio load

4. What are the clinical signs of vibriosis?

The sick shrimp is usually pale or darker color (red), with no feed in the gut.
Other major clinical signs such as disoriented shrimp swimming weakly, gathering along the edges of the pond, cloudiness of the musculature, red discoloration of the appendages and dorsal flexure at the third abdominal segment with slight rigidity.
Sometime the problem is associated with soft shell.
In later stages of the production cycle, the infection seems to be a chronic type. This is usually associated with loose shell syndrome.

5. What are all the causes of vibriosis?

Stressors such as higher salinity, poor water quality, crowding, increased ammonia level in the culture environment, low dissolved oxygen, rise in temperature, low water exchange and higher stocking density are found to be responsible for Vibriosis.

6. How to prevent the vibrio disease?

Vibriosis can be controlled with good water management and sanitation which helps to reduce the stress on shrimps.
To prevent the vibrio infection, the pond should be prepared well and the green color must be maintained to prevent benthic algae.
The pond bottom condition must be kept clean to prevent high organic matter accumulation.
Use of Probiotics (water and soil probiotic) is also suggested to control the vibriosis.

Hydrogen Sulfide (H2S)

1. What is Hydrogen Sulfide?

H2S is a toxic gas, produced in ponds by chemical reduction of organic matter accumulating in pond bottom, bottom soil often turning black and emanating a rotten smell. It is generated when sulfate consuming bacteria digest organic matter under anaerobic conditions (no oxygen) in water or under wet conditions. In a shrimp pond, the bottom layer of mud, sludge and bioflocs produce H2S.

2. How Does H2S Harm Shrimp?

The first action of H2S is to block shrimp from taking up oxygen. This weakens shrimp, makes them sluggish and increases their vulnerability, even when exposed for a short period.
When H2S levels are high, mass mortalities occur, even when exposed for a short period.
H2S can also cause tissue corrosiveness by irritating soft tissues in the gills, gut, stomach walls and hepatopancreas. H2S also stresses shrimp, lowering their resistance to infection.

3. What Causes H2S in shrimp ponds?

The following conditions will favour the generation of H2S :
In ponds with clear water before stocking, algae grows on the bottom of the ponds. Then, when phytoplankton blooms in the pond water, it blocks the light for the algae on the bottom, causing it to crash, which, in turn, leads to the generation of H2S.
Ponds with sandy or loose soil, and very deep ponds with insufficient oxygen create anaerobic conditions that lead to the production of H2S.
Ponds containing high concentrations of suspended organic matter. When the organic matter settles to the pond bottom, it creates conditions that favor H2S production.
Ponds with leaky, high-density polyethylene liners. When organic matter seeps under these liners, into an area that is devoid of oxygen, H2S is generated.
Ponds which experienced plankton crash and contain high levels of feed wastes, as well as acid sulphate ponds with low pH, and high loads of organic matter will support the release of H2S.

4. Is H2S cause mortality to shrimps?

Yes. H2S is 100 times more dangerous than ammonia and 1,000 times more dangerous than nitrite.

5. What is the safe level of H2S in Vannamei?

P. vannamei postlarvae can tolerate up to 0.0087 ppm and juveniles up to 0.0185 ppm.

6. What are all factors affecting H2S Toxicity?

Toxicity of H2S is dependent on three key parameters: pH, temperature and dissolved oxygen.
Since H2S is generated under anaerobic conditions, it will interfere with the oxygen transfer processes in the animal body. A high DO over 3 ppm in the shrimp pond could help to block H2S production.
A Combination of low pH, oxygen and temperature makes H2S more dangerous. Therefore, monitoring these three parameters is key to mitigating H2S toxicity.

7.How to Check for H2S?

Check bacterial count by TCBS agar plate in water samples collected 2-5 cm from a sludge area. Normal Vibrio will show up as green or yellow colonies; sulfate reducing bacteria will show as a black colony. If you see a black colony, it means H2S is being generated. Immediate action should be taken.

8. How to Prevent H2S?

To prevent H2S toxicity, the farmer should follow these guidelines :
Keep DO at the critical point (30 cm high from pond bottom and 3 m from sludge edge at 3-4 am) always over 3 ppm, from beginning to harvest of each crop.
Feed on demand.
Monitor organic matter.
Avoid farming in loose or sandy soil or in acid sulfate areas.
Keep pH between 7.8 to 8.3 during the entire crop. The daily pH range must be less than 0.4.
Check Bacterial count
Farmers should be carefull and take prompt action during heavy rains and plankton crash

9. How heavy rains causes H2S production to shrimps? What to Do During Heavy Rain?

During heavy rains, water parameters change that encourage H2S production. Rains cause low temperatures, dissolved oxygen and pH, as well as lower alkalinity and mineral levels. Sounds and waves created by wind also stress shrimp and cause them to crowd together on pond bottoms and in sludge areas, places where H2S is generated. This factors leads to mortality.
When this happens, farmers should do the following :
Stop feeding during rainy conditions.
Check water pH and apply lime if necessary to maintain optimal conditions.
Keep aerators running all the time.
Remove fresh water from the pond as much as possible.
Avoid floodwaters to enter shrimp ponds.
Have mineral and salt solubles ready to mix with feed following the rains
Apply H2S edible bacteria to control H2S

10. What to Do During a Plankton Crash to reduce H2S?

Once there is a plankton crash, pH will immediately drop. Organic matter concentrations will increase suddenly, resulting in a sudden uptake of oxygen. Toxic gases will be released and bacteria will bloom. The farmer must take the following steps :
Cut feed amounts by 50-60%.
Apply fine lime to maintain pH and to flocculate the dead plankton.
Run aerators to force organic matter into the center of your pond.
Exchange water by siphoning out center-of-the-pond sludge.
Apply H2S consuming bacteria.

11. What to Do When H2S Is Detected?

When symptoms of H2S are detected, the farmer must:
Immediately cut feed amounts by 30-40% for at least 3 days until conditions return to normal.
Increase aeration immediately (but be aware of sludge disturbance during installation of a new aerator).
Exchange water to make sure it remains clear and apply probiotics.
Apply lime immediately to increase pH to over 7.8.
Apply microorganisms that can consume H2S, Paracoccus pantothrophus, for example.

12.What are all the symptoms of shrimp affected by H2S Toxicity and causes?

Symptoms	Causes
Loose shell Syndrome	Long exposure to H2S leading to stress and lower feed consumption.
Black Gills	Exposure to H2S when shrimp Search for food at pond bottom.
Abnormal color of shrimp gill and body	Stress after long exposure to H2S
Mortality Following Moulting	When shrimp moult, they need more oxygen and stay close to sludge area. If H2S is high the moulting shrimp will die.
First morning meal, Shrimp Consumes less feed.	In the morning, Water pH and DO will be lowest with higher concentrations of H2S affecting feed Consumption.
White Fecal Disease (WFD)	H2S toxicity irritates soft tissue in Shrimp gut causing the release of fat and mucous to relieve the problem. (Caused by many factors, not only H2S toxicity)
Rotten egg smell from Pond	Gases (H2S) Bubbling in the middle of the pond. Discharge water color is black with rotten egg smell.
Sudden Phytoplankton Bloom	H2S facilitates the free release of phosphate into the water resulting in a phytoplankton bloom in 2-3 days.
High Ammonia and Nitrite	Nitrifying bacteria destroyed by H2S.

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