Evaluation of buffering potency of oyster (<i>Crassostrea gasar</i>) shells for aquaculture in the Niger delta, Nigeria

Abstract

A study was conducted to assess buffering efficiency of oyster (Crassostrea gasar) shells on acidic borehole water for fish farming. Eighteen (18), 100-litre shaded plastic tanks (3/4- filled, pH 4.0) of three replicates per treatment of 270 g buffer agent were used. There were four trials of six treatments (T) namely control (C) [T1], calcium carbonate (CA) [T2], crushed burnt oyster shells (CBOS) [T3], uncrushed burnt oyster shells (UBOS) [T4], crushed unburnt oyster shells (CUOS) [T5] and uncrushed unburnt oyster shells (UUOS) [T6]. Temperature and pH were monitored morning, afternoon and night while dissolved oxygen, calcium and alkalinity were measured once for the duration of study using standard methods. Data were subjected to analysis of variance and descriptive statistics using Microsoft Excel. The pH values of all treatments except T1 in the first and second trials were within the range of 6.5-9.0 acceptable for fish production. Buffering efficiency of CBOS, UBOS, CUOS and UUOS were similar to that of CA. This study recommends use of at least 270 g of CBOS and CUOS for treatment of 100 litres of acidic water for minimum of two days for aquaculture. Oyster shells buffer is cheap and safe for aquaculture.

Key Words: Organic fish farming, organic buffer, capability, pH, oyster shell lime assessment