Does charcoal act as a protective agent in fish nutrition to increase growth and physiological performance? A meta-analysis

Charcoal and its derivatives are widely recognised for their strong capacity to adsorb numerous intoxicants and their potential to increase aquaculture productivity. Using a meta-analysis technique, this study evaluated the effects of dietary charcoal supplementation on fish growth and physiological performance across 22 studies involving diverse species, including carnivores and omnivores. Charcoal supplementation levels, fish species and feeding behaviour, growth parameters, and physiological parameters were employed as variables and fitted via a meta-analysis random-effects model with Hedges’ g and its variance as an estimator of effect size. These results confirm that dietary charcoal significantly enhances aquaculture performance by increasing the specific growth rate, feed conversion ratio, protein efficiency ratio, weight gain, and nutrient digestibility without adverse physiological effects. Subgroup analysis revealed that activated, bamboo, and wood charcoal were particularly effective, especially in omnivorous and carnivorous fish. Charcoal notably reduced aspartate aminotransferase and increased immunoglobulin levels, suggesting benefits for liver function and immunity. Meta-regression revealed dose-dependent improvements with wood charcoal, whereas responses to bamboo and activated charcoal were variable. In summary, these findings support the potential of charcoal as a sustainable, species-specific feed additive in aquaculture.