Tilapia Topics, Disinfectant, Chlorine

Chlorine can be used to disinfect equipment, containers and water.

Chlorine products used for disinfection.

Chlorine comes as a powder, in tablets, liquid and as a gas. The non-gas powder formulations of chlorine vary in concentration of chlorine activity. Commercially available liquid chlorine, e.g. Chlorox is 5.25% by weight active calcium hypochlorite. Powder chlorine formulations are usually 65 to 70% active calcium hypochlorite.

Information about chlorine

Chlorine is used as a disinfectant in fish culture. Chlorine is a strong oxidizing agent and is highly toxic to fish. Exposure to even low levels of chlorine can cause serious damage to the gills of fish. Chlorine concentration of 0.01 mg/l will cause stress in many species of fish and levels of 0.1 to 5 mg/l will cause death.

In water chlorine occurs in two forms one being a negatively charged molecule and the other has no electrical charge. The pH of the water determines the distribution of the two forms of chlorine. A acid environment favors the formation of the neutral form while a basic pH the ionized state.

The biological activity and disinfection potential of chlorine differs between the two ionic states of chlorine. The neutral form passes readily through biological membranes and thus has much greater efficiency as a biocide. Since an acid pH increases the level of the neutral form of chlorine, decreasing the pH of water used for a chlorine solution improves the disinfectant properties of the solution.

With time the strength of chlorine in water will decrease and eventually disappear. Chemicals such as sodium thiosulfate can be added to a chlorine to convert chlorine into a non-toxic state.

Prior to disinfection of tank surfaces or equipment, thorough cleaning is suggested to remove organic debris and detrital build-up. Disinfection will be severely hampered if organic material is not first eliminated.

Chlorinated municipal water must be de-chlorinated before use. Chlorine must be removed from the new water by adding either commercial de-chlorination chemicals or 1000mg Vitamin C per 100 gallons water. If the water is treated with Chloramine^ (a more stable combination of chlorine and ammonia) then a special commercial chemical made to remove chloramine must be used or the water must be left to stand at least 24 hours after de-chlorination to allow the ammonia still present to dissapate.

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