How to Control Ammonia & Nitrite in Shrimp Ponds

How to Control Ammonia & Nitrite in Shrimp Ponds

Ammonia and nitrite are two important water-quality parameters that every shrimp farmer should monitor regularly.

They are part of the nitrogen cycle in a shrimp pond and are closely connected with feed, shrimp biomass, organic matter, oxygen, bacteria and pond-bottom condition.

When feed and organic waste accumulate, nitrogen compounds can build up. Poor oxygen conditions can further disturb the normal conversion of nitrogen compounds in the pond. FAO identifies ammonia as a product of animal metabolism and decomposition of organic matter, and notes that pH and temperature influence the proportion of ammonia present in the more toxic unionised form.

For Indian vannamei farms, the Coastal Aquaculture Authority (CAA) specifically requires routine monitoring of total ammonia, unionised ammonia, nitrite and other water-quality parameters.

What Are Ammonia and Nitrite?

The nitrogen cycle in a shrimp pond can be simplified as:

Feed & shrimp waste → Ammonia → Nitrite → Nitrate

Ammonia is produced from shrimp metabolism and the decomposition of organic matter. Under suitable conditions, microorganisms convert ammonia into nitrite and subsequently nitrate.

The process depends on the pond's biological and environmental conditions.

Simple explanation

Ammonia: Comes mainly from shrimp waste, uneaten feed and decomposition.

Nitrite: An intermediate nitrogen compound formed during the conversion of ammonia.

Nitrate: A later-stage nitrogen compound that is generally less immediately toxic than ammonia and nitrite at typical pond concentrations.

The objective is not simply to "remove ammonia" with one product. It is to keep the whole nitrogen cycle working properly.

Why Are Ammonia and Nitrite Dangerous?

High concentrations can create stress for cultured shrimp and interfere with normal growth and survival.

Ammonia is particularly important because the toxic unionised ammonia (NH₃) fraction increases as pH and temperature rise. FAO explains that the percentage of toxic unionised ammonia can change substantially with pH and temperature.

This means:

The same total-ammonia reading can represent a different level of risk under different pH and temperature conditions.

What Causes High Ammonia in Shrimp Ponds?

Several factors can contribute.

1. Overfeeding

Uneaten feed decomposes and adds organic nitrogen to the pond.

More wasted feed → More decomposition → More ammonia

This is why feed management is also water-quality management.

1. High Shrimp Biomass

As shrimp biomass increases, the amount of metabolic waste entering the pond increases.

A pond that was comfortable early in the crop may experience greater nitrogen loading later.

1. Excess Organic Matter

Organic matter can accumulate in:

Feeding areas

Pond corners

Sludge zones

Areas with poor circulation

1. Poor Dissolved Oxygen

Oxygen is important for the biological processes responsible for nitrogen conversion.

FAO notes that when dissolved oxygen becomes low, nitrate can be reduced back toward ammonia, while low oxygen also increases the toxicity concern associated with unionised ammonia.

1. Algal Crash

When a large amount of phytoplankton dies, decomposition can increase the organic load and oxygen demand of the pond.

1. Poor Pond-Bottom Condition

Black sediment, bad smell and accumulated organic matter are warning signs that the pond bottom needs attention.

What Causes High Nitrite?

Nitrite can increase when the nitrogen cycle is not functioning efficiently.

Possible contributing factors include:

High organic loading

High ammonia production

High shrimp biomass

Inadequate oxygen

Poor biological filtration or nitrification

Rapid changes in pond conditions

Ammonia vs Nitrite: Simple Comparison

What Ammonia Level Should Shrimp Farmers Watch?

This is an area where terminology matters.

CAA's general coastal-aquaculture guideline lists an optimal ammonia-N level below 0.01 ppm and nitrite-N below 0.01 ppm.

MPEDA's current farmer BMP table, meanwhile, lists total ammonia = 0.5 ppm as a practical reference and recommends morning testing.

These numbers should not be mixed together, because measurements may refer to different forms or reporting conventions.

For farmers

Always check whether your test kit reports:

Total Ammonia Nitrogen (TAN)

or

Ammonia-N

or

NH₃ / unionised ammonia

Also consider pH and temperature when interpreting ammonia results because they affect the unionised fraction

Step-by-Step Guide to Control Ammonia and Nitrite

Step 1: Test the Water First

Before adding anything to the pond, measure the water.

At minimum, check:

☐ Total ammonia

☐ Unionised ammonia, where available

☐ Nitrite

☐ pH

☐ Dissolved oxygen

☐ Temperature

☐ Alkalinity

☐ Salinity

Step 2: Recheck the Test

If the ammonia or nitrite reading is unexpectedly high:

Repeat the test.

Check the test kit expiry date.

Follow the test procedure carefully.

Verify the sample location.

Consider laboratory confirmation for an important management decision.

Step 3: Check Dissolved Oxygen Immediately

Low oxygen can make nitrogen management more difficult.

MPEDA recommends checking DO around 5–6 AM and gives 4–6 ppm as a reference range.

CAA's current L. vannamei guidance calls for DO to remain above 5 mg/L throughout the culture period.

If DO is low

Increase appropriate aeration → improve circulation → recheck DO → reassess feeding and pond conditions.

Step 4: Review the Feeding Program

This is one of the first things to investigate.

Check:

Daily feed quantity

Feed-tray response

Recent feed increases

Shrimp biomass estimate

Uneaten feed

Feed storage quality

Simple rule

Do not keep feeding the same quantity just because the feeding chart says so.

Step 5: Reduce Unnecessary Feed During Stress

If shrimp are stressed and water quality has deteriorated, continuing the same feeding quantity can add more organic matter.

MPEDA recommends reducing feeding during conditions such as low DO, plankton crash, rainfall, extreme temperature and disease outbreaks.

Step 6: Check the Pond Bottom

Inspect:

Feeding zones

Corners

Sludge areas

Central accumulation areas

Look for:

Black soil + bad smell + organic deposits

Step 7: Remove Excess Organic Matter

Where practical, remove accumulated:

Sludge

Uneaten feed

Dead organisms

Benthic organic deposits

Step 8: Improve Aeration and Circulation

Good aeration is not only about increasing oxygen.

It also helps maintain circulation and reduces stagnant areas.

Step 9: Check pH and Temperature

This is especially important when ammonia is present.

The toxic unionised fraction of ammonia rises as pH and temperature increase.

Therefore, when you get an ammonia reading, also record:

pH = ____

Temperature = ____°C

Step 10: Check Alkalinity

Alkalinity contributes to the buffering capacity of pond water and supports stable pH conditions.

MPEDA's current BMP reference for total alkalinity is 100–200 ppm.

Step 11: Review Plankton Condition

Observe:

Water colour

Transparency

pH trend

DO trend

Sudden changes in bloom density

Step 12: Maintain Healthy Biological Filtration

Beneficial nitrifying microorganisms play an important role in converting ammonia through the nitrogen cycle.

Their performance depends on environmental conditions such as:

Oxygen

pH

Temperature

Organic loading

Available surfaces for microbial growth

Step 13: Use Probiotics Carefully

Probiotics are widely used in aquaculture, but they should be part of an overall management program rather than treated as a guaranteed cure.

Before using a product, check:

Product composition

Intended application

Dosage

Storage

Compatibility with the farm system

Local regulatory requirements

Most importantly:

Do not use probiotics as a substitute for fixing overfeeding, low DO or excessive organic matter.

Step 14: Be Careful With Water Exchange

Water exchange can sometimes help manage accumulated dissolved and suspended waste, but it is not automatically the correct response to every ammonia or nitrite reading.

MPEDA's current BMP guidance emphasizes minimizing unnecessary water exchange when pond conditions are good and using appropriate screened water and reservoirs.

Before exchanging water, consider:

Incoming-water quality

Disease risk

Salinity difference

Biosecurity

Reservoir availability

Current pond condition

Applicable regulations

Step 15: Monitor Nitrite Separately

Do not assume that controlling ammonia automatically means nitrite is under control.

Continue testing nitrite.

A simple monitoring record:

Date Pond Ammonia Nitrite DO pH Temperature

Day 1 Pond 1 0.20 ppm 0.01 ppm 5.2 7.8 29°C

Day 2 Pond 1 0.25 ppm 0.02 ppm 4.8 7.9 29°C

Day 3 Pond 1 0.35 ppm 0.04 ppm 4.3 8.0 30°C

The numbers above are examples only.

The important point is to identify whether the values are increasing, decreasing or remaining stable

Step 16: Look at Trends, Not Just One Reading

Suppose ammonia readings are:

0.15 → 0.20 → 0.28 → 0.40 ppm

Even before reaching a critical value, the upward trend tells you that something in the pond is changing.

Investigate:

Feed → biomass → DO → pond bottom → plankton → water exchange → nitrogen cycling

Step 17: Check Shrimp Behaviour

Water testing should be combined with observation.

Look for:

Reduced feeding

Weak swimming

Surface activity

Unusual aggregation

Poor growth

Increased mortality

Abnormal swimming

How to Control High Ammonia: Simple Action Plan

When ammonia rises:

1. Test

Confirm the ammonia result.

1. Check pH and temperature

These affect ammonia toxicity.

1. Check DO

Low oxygen can worsen the nitrogen-cycle problem.

1. Review feed

Look for overfeeding and uneaten feed.

1. Check pond bottom

Look for sludge and organic accumulation.

1. Improve aeration

Maintain adequate oxygen and circulation.

1. Review plankton

Look for excessive bloom or sudden crash.

1. Consider appropriate water management

Only where suitable and safe.

1. Continue testing

Do not stop after one measurement.

How to Control High Nitrite: Simple Action Plan

When nitrite increases:

1. Confirm the reading.
2. Check ammonia.

High ammonia can indicate broader nitrogen-cycle loading.

1. Check DO.

Nitrogen conversion depends on appropriate environmental conditions.

1. Review organic loading.

Check feed, sludge and mortality.

1. Check alkalinity and pH.

Stable conditions support biological processes.

1. Review biofiltration/nitrification.

Determine whether biological conversion is functioning properly.

1. Recheck nitrite.

Monitor the trend after corrective actions.

Ammonia and Nitrite Management Are Connected to Feed

Feed is one of the biggest nitrogen inputs into an aquaculture pond.

Consider this simple chain:

More feed → more shrimp growth and waste + more uneaten feed → more organic matter → more nitrogen compounds

This does not mean feeding less is always better.

Ammonia and Nitrite Management Are Connected to Dissolved Oxygen

Oxygen is a major part of good pond management.

When DO falls:

Shrimp become stressed.

Decomposition can continue consuming oxygen.

Biological nitrogen conversion can become less efficient.

The overall water-quality situation can deteriorate.

Good oxygen management supports good ammonia and nitrite management.

Ammonia and pH: Why Farmers Should Check Both

This is extremely important.

A farmer may see:

Total ammonia = 0.5 ppm

But that number alone does not tell the complete risk picture.

The proportion present as unionised NH₃ changes with pH and temperature. FAO's reference tables demonstrate that the toxic fraction can become much higher as pH increases.

Therefore, whenever ammonia increases:

Check ammonia + pH + temperature together.

**Simple Ways to Prevent Ammonia and Nitrite Problems

**

1. Avoid overfeeding.

1. Use feed trays and observe feed consumption.

1. Sample shrimp regularly and update biomass estimates.

1. Maintain adequate dissolved oxygen.

1. Maintain good pond circulation.

1. Remove excessive organic matter.

1. Monitor the pond bottom regularly.

1. Watch for excessive plankton blooms and algal crashes.

1. Test ammonia and nitrite routinely.

1. Investigate the cause rather than relying on a single treatment product.

Complete Ammonia & Nitrite Monitoring Checklist

Daily

☐ Check early-morning DO

☐ Observe shrimp behaviour

☐ Check feed response

☐ Observe water colour

☐ Record unusual smell or surface activity

Routine Water Testing

☐ Total ammonia

☐ Unionised ammonia where available

☐ Nitrite

☐ pH

☐ Temperature

☐ Alkalinity

☐ DO

☐ Salinity

Pond-Bottom Checklist

☐ Check feeding areas

☐ Check corners

☐ Look for black soil

☐ Check for bad smell

☐ Look for sludge accumulation

☐ Check for uneaten feed

☐ Check for dead organisms

☐ Remove excessive organic matter

Feed Management Checklist

☐ Estimate shrimp biomass

☐ Check feed-tray response

☐ Record daily feed

☐ Check for uneaten feed

☐ Adjust feeding when shrimp are stressed

☐ Avoid feeding heavily over deteriorated bottom areas

☐ Store feed correctly

Aeration Checklist

☐ All aerators working

☐ Motors checked

☐ Paddlewheels checked

☐ Electrical connections checked

☐ Aerators positioned for circulation

☐ Backup power available

☐ Nighttime operation planned

☐ Aeration reviewed as biomass increases

What NOT to Do When Ammonia or Nitrite Is High

Don't immediately add several products.

First identify the cause.

Don't ignore low DO.

Oxygen problems can make the overall situation worse.

Don't continue heavy feeding without checking consumption.

Uneaten feed adds organic loading.

Don't rely on water colour alone.

A visually attractive pond can still have poor ammonia or nitrite conditions.

Don't use unapproved chemicals or antibiotics.

CAA regulations and applicable food-safety requirements must be followed.

Don't assume one treatment works for every pond.

Each pond has its own biomass, soil, water source and management history.

Easy Formula for Your Website

This topic would be excellent for an Aqua Culture Guide Water Quality Calculator.

Farmer enters:

Ammonia: ___

pH: ___

Temperature: ___

Nitrite: ___

DO: ___

Calculator can display:

Ammonia status

Nitrite status

DO status

Possible risk factors to check

Recommended parameters to re-test

For ammonia, the calculator should distinguish between TAN and unionised NH₃ rather than treating all ammonia readings as interchangeable.

Quick Reference Table

Parameter Reference / Point to Monitor

Total ammonia MPEDA current farmer reference: 0.5 ppm

Ammonia-N CAA general optimal level: <0.01 ppm

Nitrite-N CAA general optimal level: <0.01 ppm

Dissolved oxygen MPEDA: 4–6 ppm

pH MPEDA: 7.5–8.3

Total alkalinity MPEDA: 100–200 ppm

Conclusion

Ammonia and nitrite management starts with good overall pond management.

Instead of looking for one product that will solve the problem, focus on the complete system:

Good Feed Management

↓

Lower Organic Waste

↓

Good Dissolved Oxygen

↓

Healthy Nitrogen Cycling

↓

Better Water Quality

The most useful farmer habit is to measure regularly, record the results and investigate trends.

When ammonia or nitrite increases, check:

Feed → Biomass → DO → pH → Temperature → Alkalinity → Pond Bottom → Plankton → Nitrogen Cycle