Tilapia Topic, Aquaculture Environment, Alkalinity

As a measurement, alkalinity provides a means to assess the titratable base concentration or ability of water to resist pH change. Bicarbonates and carbonates usually make up the majority of base substances measured by alkalinity. However, other bases may contribute as well.

Alkalinity is not a direct cause of disease in tilapia, but water with low alkalinity is poor for fish culture. Low alkalinity water does not support plankton growth due to a scarcity of carbon dioxide. These waters are weakly buffered against pH change.

Alkalinities between 50 to 150 mg/L are best suited for fish culture. Values less than 50 mg/L are considered low and levels less than 20 mg/L very low. Alkalinity greater than 200 mg/L is high. Alkalinity changes little on a daily cycle and measurement of source water need only be done on an occasional basis; unless a situation arises which is characterized as a problem with plankton productivity. Alkalinity can be readily measured by commercially available water test kits.

Agricultural limestone can be added to pond water to increase the total alkalinity if alkalinity level is below 50 mg/L. If the total alkalinity is higher than this lime treatment will probably not appreciably increase alkalinity of the water. Dosage procedures for lime treatment are given in the Treatment Module of HAMES.

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