Feeding biochar or charcoal increased the growth rate of striped catfish (Pangasius hypophthalmus) and improved water quality

A 90 day feeding trial was conducted to determine the effects of biochar and charcoal on water quality and on growth performance of striped catfish (Pangasius hypophthalmus) raised in tanks. The five treatments in a completely randomized design with 4 replicates were: NBC (no biochar or charcoal), BF (biochar in feed), CF (charcoal in feed), BW (biochar in water) and CW (charcoal in water). Growth rates were increased 36% by adding biochar to the feed and by 44% with charcoal. There were no benefits from adding either biochar or charcoal to the water. In contrast, adding charcoal to the water had a negative effect on feed intake, growth rate and survival. The ratio of weight to length in the fish at the end of the experiment was 25% greater when biochar or charcoal was added to the feed, indicating an enhanced flesh to bone ratio due to the faster growth rate with addition of biochar or charcoal.Levels of ammonia nitrogen (TAN), nitrite (NO2-, phosphate (PO43-) and chemical oxygen demand (COD) in the tank water were reduced by adding biochar or charcoal to the feed, but not to the water. The role of biochar (and charcoal) in facilitating the formation of biofilms as habitat for gut microbiota could be the explanation for the improved growth rates recorded with biochar and charcoal added to the diet.