The document outlines key criteria for soil and water quality in aquaculture. Ideal pond soils have a neutral pH between 6.0-8.0, C:N ratio of 10-15, and nutrient levels of 30 ppm phosphorus and 250 ppm nitrogen. Water quality should have 5-20 ppm BOD, 40-60cm Secchi disc visibility, and 5-10 ppm carbon dioxide. Dissolved oxygen should be above 5 ppm for normal fish survival and growth. Proper site selection and management through liming, fertilization, aeration, and water exchange are necessary to prevent soil and water quality issues.

1. SOIL AND WATER QUALITY
CRITERIA

2. SOIL AND WATER CRITERIA/REQUIREMENTS FOR AQUACULTURE
• Important - site characteristics
• Bottom soils - undesirable - Potential acid sulphate soils, saline soils, high organic
matter content, excessive porosity etc
• Poor quality water - highly acidic, alkaline, turbid, high BOD, rich in nutrients and
organic matter, high in suspended solids or polluted with industrial or agricultural
chemicals
• Higher amount of nutrients and organic matter due to excessive organic menuring
and feed wastage - lead to poor water quality and bottom soil condition

3. WATER QUALITY CRITERIA IN AQUACULTURE
• Influence greatly on the growth and survival of aquatic organism.
Dissolved oxygen of water
• The optimum dissolved oxygen - of 5.0 mg/l
• A fish might survive 0.5 ppm DO for few hours
• An average condition, 3.0 ppm DO or less regard as hazardous for fish

4. Temperature of water
• Temperature sets the pace of fish metabolism by controlling molecular dynamics
(defeasibility, solubility, fluidity) and biochemical reaction rates
• The optimum temperature range for several cold water and warm water fishes are
14-18o C and 24o-30o C respectively
Effects of Do levels on fish production
DO (ppm) effects
< 1.0 lethal on exposure for more than few hours
> 1.0 – 5.0 fish survive but poor growth
> 5.0 normal survival and growth

5. BOD5
• The biochemical oxygen demand (BOD) - the amount of oxygen required to
microorganisms to decompose the organic matter in a water sample under specific
condition of the pond management
• Has direct bearing on the oxygen balance of water
• BOD5 values in fish ponds varied between 5 – 20 ppm
• The optimum BOD5 value is 10 – 20 ppm for fish ponds

6. Turbidity of water
• Turbidity - due to suspended soil particles, Planktonic
organism and humic substances
• The optimum Secchi disc visibility of fish ponds is considered to be 40-60cm.
Ammonia of water
• Fish are very sensitive to unionized ammonia (NH3-N); optimum range - 0.02-
0.05mg/l
Hydrogen sulfide in water
• Fresh water fish ponds should be free from hydrogen sulfide
• At concentration of 0.01mg/litre of hydrogen sulfide fish loose its equilibrium and
subjected to sub lethal stress

7. pH
• pH - measure of hydrogen ion concentration in water and indicate how much
water is acidic or basic
• Water pH - affects metabolism and physiological process of fish
• Considerable influence on toxicity of ammonia and hydrogen sulfide as well as
solubility of nutrients and thereby water fertility
pH Effect
4.0 Acid death point
4-6 Slow growth
6-9 Best for growth
9-11 Slow growth, lethal to fish
overlong period of time
11+ Alkaline death
Effect of pH on fish

8. Total alkalinity
• The ideal range of total alkalinity for fresh water fish ponds is 60-300mg/liter as
CaCO3
Total hardness
• Total hardness for fresh water fish ponds should be greater than 40mg/litre as
CaCO3
Carbon dioxide
• Fresh water fish ponds should contain a low concentration of free CO2 below 5 .0
mg/litre
• In intensive aquaculture free CO2 level may fluctuate between 5 and 10 ppm with
at ill effects on fish

9. SOIL QUALITY CRITERIA FOR AQUACULTURE
• Bottom soil - determines the productivity of a pond
• The productivity of ponds - depends on the availability of different nutrients
• Bottom soil is - Chemical Laboratory of the Pond

10. Soil Texture
• The nature and its properties of the parent material determine the soil texture
• An ideal pond soil - should not be too sandy to allow leaching of the nutrients or
should not be too clayey to keep all the nutrients absorbed on to it

11. Cation exchange capacity
• It is the total quality of cations which a soil can adsorb by cation exchange is
termed as C E C of the soil
• Expressed as milli equivalents / 100 gm soil (meq / 100 gm of soil )
• Higher C E C - more concentration of easily exchangeable
• The cations are called exchangeable bases.
• Ca++, Mg++, Na+ and K+ ions.
– Water holding capacity – capacity of soil to hold water; Clay-silt soils are best
for fish ponds
– Soil porosity, particle density, bulk density - physical quality’s of pond soils
– Help to aeration, filtration, percolation, adsorption of nutrients etc

12. Soil acidity
• The ideal range of soil pH - 6.0-8.0
• Water passing over acid soil tends to be a acidic with low alkalinity and hardness
• High concentration of metal ions particularly aluminum (A1+++) and Iron (Fe+++) to
soil acidity
• Acid ponds do not respond well to fertilization

13. Acid sulphate soils
• Acid sulphate soils from mine spills and coastal mangroves contain high levels
phyrite (Fe82 1-6%)
• Sediments containing pyrites on oxidation results in sulfuric acid
• Sulfuric acid reduces the pH of water when pond is filled
• Acid sulphate soils usually originate is pond dykes

14. Bottom soil oxidation
• Aeration and water circulation are beneficial in improving bottom soil oxygenation
• The surface layer of soil may still become anaerobic in intensive fish culture ponds
due to settlement of suspended particulate matter

15. Soil reaction (pH)
• One of the most important factors for maintaining pond productivity - controls
most of the chemical reaction in the pond environment
• Near neutral or slightly alkaline pH - ideal for fish production
• If the pH is too low - strongly acidic - reduce the availability of key nutrients in the
water and lower the pond productivity

16. Organic Carbon Content
• Acts as the source of energy for bacteria and other microbes that release nutrients
through various biochemical processes
• Pond soils with less than 0.5% Organic carbon - unproductive
• 0.5-1.5% and 1.5-2.5% Organic carbon - medium and high productivity respectively
• Organic carbon - more than 2.5% - may not be suitable for fish production

17. Carbon to nitrogen ratio
• C: N ratio of soil influences the activity of soil microbes
• Affects the rate of release of nutrients from decomposing organic matter
• Nutrient release - very fast - C:N ratio - less than 10
• Nutrient release - medium- C:N ratio - 10-20
• Nutrient release – More - C:N ratio – more than 20
• Soil C:N ratios between 10 and 15 are considered favorable for aquaculture
• Ratio of 20:1 or narrower gives good results

18. Nutrients
• Nitrogen, phosphorous and potassium - major nutrients required by
phytoplankton
• Pond soil with 30 ppm, 30-60 ppm, 60-120 ppm and more than 120 ppm available
phosphate (P2O5) - high productive
• Ponds with less than 250 ppm available soil nitrogen - low productivity
• Soil nitrogen concentration - 250 to 500 ppm and above 500 ppm - medium and
highly productive respectively
• Relatively small amounts of potassium are needed in fish ponds

19. • The best method for preventing soils and water quality problems is aquaculture
ponds is to select a site with good soil and an adequate supply of high quality
water
• If this is done, liming, fertilization and aeration can prevent most soil and water
quality imbalances
• Proper pond management viz. liming, fertilization, aeration, water exchange and
bottom soils drying and oxidation are the keys to improve soil and water quality in
ponds

20. REFERENCES :
1. The nature and properties of soils (7th edition 1969) by Harry O. Buckman and Nyle
C Brady
2. Soils and soil fertility (5th edition 1993) by Frederick R.Troch and Louis M
Thompson
3. Methods in environmental analysis - water, soil and air by P.K. Gupta (2007)