<b>Alternative liming blends for fish culture</b>

Abstract

Calcium carbonate (limestone) is a safe but slow-acting product for aquaculture liming. Calcium oxide (lime) is a fast-acting but dangerous product. It would be interesting to have simultaneously a safe and fast-acting liming product. The present work aimed to evaluate two alternative liming blends for tilapia culture. The culture water was initially acidified with HCl. Next, the same quantity of CaCO₃ (control), Na₂CO₃+CaSO₄ or Na₂CO₃+CaCl₂ was applied to the culture water. There were also non-limed tanks. One hundred and twenty Nile tilapia juveniles (1.6 ± 0.1 g) were stocked in twenty 250-L culture tanks for 10 weeks. All products used were similarly efficient in increasing the alkalinity of water. The probable better environment for algal growth in the limed tanks caused an increase in the DO₂ concentrations and a decrease in CO₂, total ammonia nitrogen, nitrite and phosphorus, in relation to the non-limed tanks. The highest final body weight of fish was observed in the Na₂CO₃+CaCl₂ tanks. The lowest final body weight was verified in the CaCO₃ tanks. It was concluded that the alternative blend of Na₂CO₃ plus CaCl₂ is a better liming product than the standard CaCO₃ for Nile tilapia culture.