Potential of marine gastropod (<i>Thais coronata</i>) shells as alternative buffer to calcium carbonate for fish farming in the Niger Delta, Nigeria

Abstract

A study was conducted to evaluate buffering potency of rock shells (Thais coronata) on acidic borehole water for aquaculture. Eighteen (18), 100-litre plastic tanks placed on shaded outdoor concrete tanks and three-quarter filled with acidic borehole water (pH 4.0) of three replicates per treatment of 270 g buffer agent were used. The treatments (T) namely control (C) [T1], calcium carbonate (CA) [T2], crushed burnt rock shells (CBRS) [T3], uncrushed burnt rock shells (UBRS) [T4], crushed unburnt rock shells (CURS) [T5] and uncrushed unburnt rock shells (UURS) [T6] were used for four trials. Temperature and pH were monitored morning, afternoon and night while dissolved oxygen, calcium and alkalinity were measured once for duration of study using standard methods. Data were analyzed using Microsoft Excel for analysis of variance and descriptive statistics. pH steadily increased from 4.0 to acceptable range of 6.5-9.0 in all treatments except T1 at the end of trials. All shell forms buffered the acidic water but crushed burnt rock shells are preferable to others in terms of fish health and food safety. Dissolved oxygen, calcium and alkalinity values were within acceptable limit. The study therefore suggests at least 270 g shell of any form as organic buffer for aquaculture.