Hydrated lime is not as suitable as agricultural limestone for increasing pH and total alkalinity in soft water ponds. However, small amounts of hydrated lime may be applied during dry summer months to increase alkalinity for several weeks in ponds that have such high water exchange rates during wetter months that conventional applications of agricultural limestone are ineffective. Hydrated lime is an effective sterilant for damp pond bottoms. It will also remove carbon dioxide from water. Hydrated lime is not an oxidizing agent, so it will not destroy organic matter in mud or water. The biochemical oxygen demand (BOD) of water may be reduced by large applications of hydrated lime because the lime increases pH to levels toxic to microorganisms. The concentration of hydrated lime necessary to reduce BOD will retard photosynthesis and will harm fish. Although hydrated lime can be used to raise pH and kill fish, its potential as a fish eradicant needs further study. Hydrated lime is not as effective as alum in coagulating clay turbidity. There is no evidence that hydrated lime will reduce problems with off-flavor in fish.
