Generally dolomitic lime is used, but if high quality calcitic lime or calmag lime is available and cheaper, they may be used. Hydrated lime, slaked lime, slag, builders lime and burnt lime have been incorrectly recommended as a pond liming material. These forms of lime are short-lived and react rapidly, causing water quality problems. This, in turn, can cause fish kills from levels that are too high. The best time to apply lime is in fall or winter.
Limestone takes four to six weeks to adjust water quality.
Ponds should not be limed and fertilized simultaneously since the calcium in lime will bind with phosphorus in fertilizer and make phosphorus, the limiting nutrient in ponds, unavailable for use. Lime is applied to the pond bottom soil, not the water, so limestone should be evenly distributed over the bottom of the pond. It is best if lime is applied immediately after pond construction, before ponds are flooded. Mechanized agricultural lime spreaders can be used at this time and greatly reduce manual labor. After the pond is filled, mechanized equipment can continue to be used, if the pond is small and there are very few obstructions around the pond or if the spreaders can cover at least 60 percent of the pond bottom.