Biofloc technology: a new approach to zebrafish (Danio rerio) larval culture

Abstract

The objective of this experiment is to use Biofloc as an alternative cost-effective technology on the growth and survival rate in Zebrafish (Danio rerio) larvae. Before starting the experiment, detritus water was collected from Zebrafish´s broodstock tank by siphoning, which served as the main nutrient source. This material included uneaten food and feces from adult zebrafishes, providing nutrients for a biofloc food chain to support newly hatched larvae. Ammonia (NH3) in detritus water was measured to determine the amount present in order to set up Biofloc culture with a Carbon/Nitrogen ratio of 10:1, honey (82% C) was used as the main carbon source and infusoria, N-fixing bacteria, and a brewer´s yeast culture derived from Guiness Stout were added to enrich the Biofloc microbial community for 1 week. Four 2L beakers were set up and 100 larvae (3.55 ± 0.08 mm) with 120 hours post fertilization (hpf) were stocked per each one; total length was measured at the beginning of the experiment; temperature was maintained at 28 ± 1 °C, color water and pH were measured daily, while Ammonia (NH3) was measured once a week; the abundance of protozoa and other microorganisms was checked once a week. The survival rate was 45 ± 6.06 (%) and final total length was 6.51 ± 0.27 (mm), water quality obtained for pH was 7.58 ± 0.07, and Ammonia (NH3) was 0.09 ± 0.04 (mg/L). Finally, the cost of the carbon source used in the experiment was calculated to be 0.005 US$ per 2L culture system. Biofloc system is relatively inexpensive and provides a sufficient culture environment to support the growth and survival of zebrafish larvae, while avoiding the discharge of wastes from the broodstock colony.