How to use quicklime in rice field eel farming

The chemical name of quicklime is calcium oxide (CaO). Because it is cheap and abundantly available, when it dissolves in water it reacts chemically with water to produce a large amount of an alkaline substance (calcium hydroxide), raising the pH of the water and thereby inhibiting or killing bacteria. It is widely used in aquaculture.

In rice field eel farming, the usual concentration used is 25 ppm (25 g per 1 cubic meter of water). The method of application in the eel pond is: weigh out the corresponding weight of quicklime, add it to water (for example in a plastic bucket holding water), stir it with a tool so that it dissolves fully, let it stand for a little while to clarify, then take the clear liquid on top and splash it on.

It should be noted that the dosage of quicklime is fairly strict, and the amount must not be increased arbitrarily, otherwise it may harm the rice field eels in the pond. Director Pan Jianlin and Professor Xu Zaikuan of the Jiangsu Provincial Institute of Freshwater Fisheries and others conducted tests on this. The test situation was: when rice field eels were stocked in quicklime water at a concentration of 50 ppm, the eels immediately became restless and dashed about wildly toward the water surface, and this phenomenon continued until just before death. More flocculent matter appeared in the test water; this was the product of the reaction between the mucus on the body surface of the rice field eels and the quicklime. All dead rice field eels secreted large amounts of mucus on the body surface, had red and swollen anuses, patchy or lumpy red spots on the neck, congestion of the head, and congestion of the gill cavity with clotted blood clots in it. Even changing to clean water after about 2 hours could not stop the deaths. In the test group with a slightly lower quicklime concentration, the mortality of the rice field eels within 5 hours and 24 hours was significantly reduced, but as time went on, the cumulative mortality rose. In the test group treated at 50 ppm, the mortality over 7 days reached 100%. Therefore, when using quicklime as a disinfectant, the amount of water must be calculated accurately and the weight must be measured accurately, and the maximum concentration is best kept no higher than 30 ppm. After using quicklime to clear a pond or disinfect an eel pond, the chemical action must be fully eliminated before use, otherwise the survival rate of the rice field eels will be affected.

Good-quality quicklime is lumpy and gives off a large amount of heat when dissolved in water; if the amount of water is small it will bring the water to a boil, while dissolving completely in the water with few or no impurities. Some trainees buy slaked lime (which has already reacted with water and is in powder form); it no longer gives off heat after entering water, and this kind of lime has a poor disinfecting effect, so it is recommended not to use it.

Trainees who cannot buy reliable-quality quicklime locally can use the "Eel Treasure No. 2" provided by our company instead. Although the cost is a bit higher, the efficacy is more stable and it is safer to use. The usual dosage is: 2 ml per 1 cubic meter of water.