How to Manage Water Quality in Vannamei Farming

Vannamei Shrimp Water Quality: Best Parameters & Ideal Range

Water quality is one of the most important factors in vannamei shrimp farming. Shrimp live continuously in the pond environment, so changes in oxygen, temperature, pH, salinity and other parameters can affect feeding, growth, stress and overall pond performance.

Good water-quality management is not about maintaining one parameter at the correct number. The objective is to keep the overall pond environment stable and identify unfavorable changes early.

Why Is Water Quality Important in Vannamei Farming?

Poor water quality can create stress for shrimp and can make other farm-management problems more difficult to control.

Important factors include:

Dissolved oxygen → Temperature → pH → Salinity → Alkalinity → Ammonia → Transparency → Water colour

CAA guidance for SPF L. vannamei specifically calls for routine monitoring of pH, alkalinity, dissolved oxygen, total ammonia, unionised ammonia, nitrite, nitrate, total nitrogen, phosphorus, BOD and COD, in addition to shrimp health and bacterial monitoring.

Ideal Water Quality Parameters for Vannamei Shrimp

According to MPEDA's current farmer guidance

Dissolved Oxygen (DO)

Ideal reference: 4–6 ppm

Dissolved oxygen is one of the most important parameters in a shrimp pond.

Shrimp require oxygen for respiration, and oxygen conditions can change substantially between daytime and nighttime.

Signs of oxygen stress

Watch for:

Shrimp swimming near the surface

Weak activity

Reduced feeding

Shrimp gathering near water inlets or aerators

Increased early-morning stress

How to manage DO

Use:

Adequate aerators

Proper aerator positioning

Good water circulation

Biomass-based aeration planning

Regular early-morning DO testing

Water Temperature

Ideal reference: 28–32°C

Temperature affects shrimp metabolism, feeding activity and overall pond biology.

MPEDA recommends measuring temperature at approximately 6 AM and 3 PM, allowing farmers to observe both morning and afternoon conditions.

Why monitor morning and afternoon?

The pond can experience a significant daily temperature cycle.

Recording both readings helps identify:

Daily temperature changes

Unusual heat

Sudden weather-related changes

Conditions that may affect shrimp feeding

Avoid relying on a single temperature reading.

Temperature management

Farmers should focus on:

Maintaining sufficient water depth

Avoiding unnecessary disturbance

Monitoring during extreme weather

Adjusting feeding when shrimp activity changes

Maintaining adequate aeration

1. pH

Ideal reference: 7.5–8.3

pH is one of the most important measurements in shrimp culture because it can change considerably between morning and afternoon.

MPEDA recommends checking pH at approximately 6 AM and 3 PM and advises keeping daily pH fluctuation below 0.5.

Why does pH change?

Phytoplankton and other biological activity affect carbon dioxide and therefore can cause daily pH movement.

Typically:

Morning → lower pH

Afternoon → higher pH

Large fluctuations are more concerning than a small normal daily change.

High pH

MPEDA identifies over-liming and excessive plankton bloom as potential causes of high pH.

Low pH

Low pH can occur in poorly buffered water and under certain soil and water conditions.

The response should be based on the actual pond condition rather than automatically adding a large quantity of any chemical.

1. Salinity

MPEDA reference: 10–25 ppt

Salinity indicates the concentration of dissolved salts in the water.

MPEDA lists 10–25 ppt as its reference range for vannamei culture and recommends measuring salinity with a refractometer.

When can salinity change quickly

Heavy rainfall

Freshwater inflow

Evaporation

Water exchange

Changes in source-water salinity

After heavy rain

Check salinity rather than assuming the pond remains unchanged.

Total Alkalinity

MPEDA reference: 100–200 ppm

Alkalinity is an important component of pond buffering and helps stabilize pH.

MPEDA recommends maintaining total alkalinity between 100 and 200 ppm in its vannamei BMP guidance.

What should farmers do?

Test alkalinity routinely and make adjustments based on:

Water chemistry

Soil condition

Salinity

Shrimp biomass

pH trend

Do not apply large amounts of lime or other mineral products simply because pH changes once. First measure pH + alkalinity + the daily trend.

Ammonia

MPEDA reference: Total ammonia 0.5 ppm

Ammonia is a major water-quality concern in shrimp ponds.

It can originate from:

Shrimp waste

Uneaten feed

Decomposing organic matter

High stocking biomass

Poor pond-bottom condition

MPEDA recommends testing total ammonia in the morning

Total ammonia vs unionised ammonia

The ammonia measured in water exists in different chemical forms. The unionised form (NH₃) is particularly important when assessing toxicity.

The proportion of unionised ammonia changes with factors such as pH and temperature.

Nitrite

Nitrite should also be included in a good shrimp-farm water-quality program.

Nitrite problems can be associated with:

High organic loading

Incomplete nitrogen cycling

High stocking biomass

Poor water management

When nitrite increases, review the entire pond system instead of treating the number in isolation.

Check:

Feed → Biomass → Organic load → Aeration → Water quality → Pond bottom

Water Transparency

MPEDA reference: 30–40 cm

Transparency is commonly measured with a Secchi disc.

MPEDA recommends measuring transparency around 12 noon and provides 30–40 cm as the reference range in its farmer guidance.

Very clear water

May indicate insufficient plankton development.

Very low transparency

May indicate excessive plankton or suspended matter.

The transparency reading should therefore be interpreted together with water colour, pH, DO and pond observations.

Water Colour

Preferred reference: Green or brown

MPEDA identifies green or brown as the preferred water colour in its shrimp-farming guidance.

A stable plankton community can provide a more suitable pond environment.

However:

Dark green water does not automatically mean a healthy pond.

Calcium and Magnesium

Mineral balance is another important part of vannamei pond management.

MPEDA's BMP guidance highlights the importance of calcium and magnesium in vannamei farming and gives a general Ca:Mg ratio of 1:3 as a management reference

Mineral management can become particularly important when:

Salinity is low

Water source has low mineral content

Shrimp show growth or molting concerns

Large amounts of water are exchanged

Water Hardness

Water hardness represents the concentration of certain dissolved minerals, particularly calcium and magnesium.

Although hardness is not included in MPEDA's short farmer reference table above, ICAR-CIBA's multiparameter water-quality testing program includes calcium, magnesium and total hardness among the parameters that can be monitored on farms.

BOD and COD

CAA's vannamei guidance includes BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) among the water-related parameters to be routinely monitored.

These are particularly relevant when evaluating organic pollution and wastewater management.

It is important to distinguish:

Pond water-quality management from effluent discharge standards.

Complete Vannamei Water Quality Table

Step-by-Step Daily Water Quality Monitoring

Check DO in the Early Morning

Measure DO around 5–6 AM.

This is one of the most important daily checks because oxygen can be low after nighttime respiration.

Record:

DO = ____ ppm

MPEDA recommends this monitoring time.

Measure Morning Temperature

Take the temperature around 6 AM.

Record:

Temperature = ____ °C

This becomes your baseline for comparison with the afternoon reading.

Measure Morning pH

Check pH around 6 AM.

Record:

Morning pH = ____

Measure Afternoon pH and Temperature

Repeat the measurements around 3 PM.

Record:

Afternoon temperature = ____ °C

Afternoon pH = ____

Now compare morning and afternoon readings.

This helps identify daily fluctuations rather than looking at only one measurement.

Check Salinity

Use a properly calibrated refractometer.

Record:

Salinity = ____ ppt

Check more frequently when:

Heavy rain occurs

Water is exchanged

Source-water salinity changes

The farm operates at low salinity

MPEDA lists refractometer testing as the method for salinity measurement in its BMP table.

Check Alkalinity

Use a reliable alkalinity test kit or laboratory method.

Record:

Total alkalinity = ____ ppm

Track the trend rather than waiting until a serious pH problem appears.

Check Ammonia

Test ammonia in the morning according to the MPEDA monitoring schedule.

Record:

Total ammonia = ____ ppm

If the value rises, investigate:

Feed quantity

Uneaten feed

Shrimp biomass

Pond-bottom condition

Aeration

Organic loading

Do not simply add a water-treatment product without investigating the cause.

Measure Transparency

Use a Secchi disc around noon.

Record:

Transparency = ____ cm

Compare the reading with previous days rather than interpreting one reading alone.

Observe Water Color

Look at the pond during daylight.

Record:

Water colour = Green / Brown / Clear / Dark / Other

Also check for:

Sudden colour changes

Surface scum

Excessive algae

Foam

Unusual smell

Record Everything

A water-quality log can look like this:

Date DO Temp AM Temp PM pH AM pH PM Salinity Alkalinity Ammonia Transparency

Day 1 4.8 28.2 31.0 7.7 8.0 15 140 0.20 35

Day 2 4.6 28.5 31.3 7.6 8.1 15 138 0.22 34

Day 3 4.2 28.8 31.5 7.5 8.2 14 136 0.25 32

What Should You Do When Water Quality Changes?

When DO Falls

Check aerators → increase appropriate aeration → reduce feeding if necessary → observe shrimp → continue monitoring.

When pH Becomes High

Check:

Plankton density

Transparency

Alkalinity

Liming history

Daily pH fluctuation

MPEDA identifies excessive plankton bloom and over-liming as possible causes of high pH.

When Ammonia Increases

Review:

Feed → biomass → oxygen → pond bottom → organic loading

Avoid automatically adding multiple products without determining why ammonia increased.

After Heavy Rain

Immediately review:

Salinity → pH → temperature → DO → alkalinity

Rain can change pond conditions rapidly.

Water Quality and Feed Management Are Connected

Water quality cannot be managed separately from feeding.

Excess feed can increase organic loading, which can contribute to deterioration of pond conditions.

MPEDA states that feed represents approximately 50–60% of operating cost and advises reducing feeding during low DO, plankton crashes, rainfall, molting, extreme temperatures and disease outbreaks.

Therefore:

Poor feeding → more waste → higher organic load → greater water-quality pressure

Good feeding management helps support good water quality.

Common Water Quality Mistakes

1. Checking DO only in the afternoon

Early morning is an important time for DO measurement.

1. Checking pH only once a day

Morning and afternoon measurements show daily fluctuation.

1. Treating numbers instead of causes

A high ammonia reading is a signal to investigate the pond system.

1. Ignoring pond-bottom condition

Black soil and bad odors can indicate deterioration. MPEDA recommends weekly bottom checks.

1. Over-fertilizing to make water dark green

Excessive plankton can reduce nighttime oxygen.

1. Changing water unnecessarily

MPEDA recommends minimizing water exchange when pond conditions are good and shrimp are healthy.

1. Not calibrating equipment

A faulty meter can lead to incorrect management decisions.

1. Not recording results

A single number is less useful than a trend.

1. Ignoring rainfall

Rain can rapidly change salinity and other water conditions.

1. Waiting until shrimp show stress

Regular monitoring allows earlier detection.

Best Water Quality Monitoring Schedule

Every Morning

DO → Temperature → pH → Ammonia → Shrimp behaviour

Afternoon

Temperature → pH → Water colour

Any Time / Routine Schedule

Salinity → Alkalinity

Noon

Transparency

Weekly or According to Farm Risk

Nitrite → Nitrate → Calcium → Magnesium → Hardness and other laboratory parameters

Vannamei Water Quality Checklist

Daily

☐ DO checked

☐ Temperature checked

☐ Morning pH checked

☐ Afternoon pH checked

☐ Shrimp behaviour observed

☐ Water colour checked

☐ Transparency checked

Routine

☐ Salinity checked

☐ Alkalinity checked

☐ Ammonia checked

☐ Nitrite checked

☐ Pond-bottom condition checked

☐ Aerators inspected

After Rainfall

☐ DO checked

☐ pH checked

☐ Salinity checked

☐ Temperature checked

☐ Alkalinity reviewed

☐ Shrimp activity observed

Simple Water Quality Targets for Farmers

For a quick reminder:

DO

4–6 ppm

Temperature

28–32°C

pH

7.5–8.3

Salinity

10–25 ppt

Alkalinity

100–200 ppm

Total Ammonia

0.5 ppm reference

Transparency

30–40 cm

Water Colour

Green or brown

These figures are from MPEDA's current Better Management Practices for shrimp farming.

Important Note on "Ideal" Water Quality

Farmers should avoid thinking of water quality as a set of isolated numbers.

For example:

pH = 8.2 by itself may not tell the complete story.

You also need to know:

DO

Alkalinity

Temperature

Transparency

Plankton condition

Ammonia

Nitrite

Shrimp behavior

The most useful approach is therefore:

Measure → Record → Compare → Identify the cause → Take appropriate action → Recheck

Conclusion:

Good water quality management is the foundation of successful vannamei shrimp farming.

Farmers should pay particular attention to:

Dissolved oxygen, temperature, pH, salinity, alkalinity, ammonia, transparency and water colour.

The most important practice is not simply achieving a target number once. It is maintaining stable conditions and identifying changes early.