Page 51 - fish_farms_curriculum

5.7. Lime Content and Properties

Liming is an effective tool in fish production and pond management. However, lime is

randomly used to describe two different types of materials used for very different purposes.
Agricultural limestone refers to calcite (calcium carbonate) and dolomite (calcium magnesium

carbonate). Calcium and magnesium compounds increase the overall water hardness, which is
essential for the health of many water species. The carbonate component raises total alkalinity

and pH, buffers daily fluctuations in pH, increases microbial activity in the pond soil, and

increases the availability of phosphorus to phytoplankton. Pool water with a total alkalinity of
less than 20 ppm can benefit from calcification. Hydrated lime (calcium hydroxide) is an

inexpensive and effective pool sterilizer that quickly and dramatically raises the pH above
tolerable levels for aquatic organisms. It should be used with caution, avoiding contact with

the applicator, and should never be used in pools containing desirable fish.

Lime application in fish ponds has three main purposes:

1. Increasing the utility of nutrients.

2. To increase pH and buffer against daily pH fluctuations.

3. Sterilizing pools before stocking.

(While these applications use lime, they contain different chemical compounds.)

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