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 mg/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. Water pH - affects metabolism and physiological process of fish
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
Effect of pH on fish 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

8. Total alkalinity
The ideal range of total alkalinity for fresh water fish ponds is mg/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
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
% and % 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
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, ppm, 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 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)