Pond Construction, Soil and Water Quality Management
Site and pond type
Choose level land with clay-loam soil, adequate water, no flooding, and road or market access. Nursery ponds are small and shallow; rearing ponds are larger; stocking ponds are larger still. A reliable water source and a drainable bottom matter more than perfect shape.
Soil and water rules
- Soil pH below 6.5 needs agricultural lime; apply in split doses and wait 7-10 days before fertilizing.
- Pond water pH 6.5-8.5 is workable; measure at the same time of day because pH rises in the afternoon.
- Dissolved oxygen should stay above 5 mg/L; early-morning lows are the danger point.
- Total ammonia is not the toxic measure; un-ionized NH3 rises with high pH and temperature and should be kept very low.
- Fertilization encourages natural food but must not be paired immediately with lime.
Worked example
A 0.1 ha pond averages 1.5 m depth, so volume = 1,000 m2 x 1.5 m = 1,500 m3. If lime is prescribed at 200 kg/ha, the dose is 0.1 x 200 = 20 kg. If the pond is later fertilized, apply after the waiting period. Reasoning: area, not volume, drives the per-hectare lime dose in this convention; volume is used for water-treatment products.
Traps
- Applying lime and fertilizer on the same day.
- Treating total ammonia as toxic without checking pH.
- Measuring DO only at noon.
- Using pond volume for a dose stated per hectare.