Phytoterapy has been used in aquaculture for disease control, especially the Terminalia catappa that demonstrated excellent antimicrobial potential. The aquaculture commonly uses the extract obtained at room temperature, but the hot aqueous extract (HAE) and its effects on the fish are still unknown. This study aimed to determine the lethal concentration (LC₅₀) of HAE from Terminalia catappa in juvenile fish Colossoma macropomum as well as to evaluate hematological and histological parameters. Two extracts were obtained in different temperatures and submitted to HPLC. Despite both extracts presented the similar chemical compounds, HAE showed higher levels of compounds and then it was selected. For acute toxicity test, six different extract concentrations (0.00, 0.10, 0.20, 0.30, 0.40, and 0.50 g/L) in triplicate was used. At the end of the experiment, all fishes were submitted to hematological and histological analysis. The LC₅₀ was determined using trimmed Spearman-Karber method, and water quality (pH, temperature, DO, electrical conductivity, and ammonia) were measured. The results were submitted to ANOVA followed by Tukey’s test (p < 0.05). The HAE showed LC₅₀ of 0.41 g/L with changes on water parameters, such as pH and conductivity, as well as the fish behavior. HAE also altered hematologic parameters and showed histopathological changes on the gill and liver using high concentration of the extract or longtime exposure in low extract concentrations. Despite HAE showed higher concentration of compounds, it remains considered as a practically non-toxic product. Nonetheless, water quality, hematological, and histological alterations must be considered to determine concentrations and strategies of application in vivo.

植藻已被用于水产养殖的疾病控制中，尤其是表现出极佳抗菌潜力的榄仁木。水产养殖通常使用在室温下获得的提取物，但仍不清楚热水提取物（HAE）及其对鱼的影响。本研究旨在确定致死浓度（LC ₅₀从HAE的）榄仁在幼鱼淡水白macropomum以及评估血液学和组织学参数。在不同温度下获得两种提取物，并进行HPLC分析。尽管两种提取物都显示出相似的化学化合物，但HAE显示出较高的化合物含量，因此选择了该化合物。对于急性毒性测试，使用了六种不同浓度的提取物（0.00、0.10、0.20、0.30、0.40和0.50 g / L），一式三份。在实验结束时，所有鱼类均接受了血液学和组织学分析。使用修整的Spearman-Karber方法确定LC ₅₀，并测量水质（pH，温度，DO，电导率和氨水）。将结果提交给ANOVA，然后进行Tukey检验（p <0.05）。HAE显示LC ₅₀浓度为0.41 g / L，随水参数（例如pH和电导率）以及鱼类行为的变化而变化。高浓度提取物或低浓度提取物长期暴露后，HAE还改变了血液学参数，并显示了腮和肝脏的组织病理学变化。尽管HAE表现出较高的化合物浓度，但仍被认为是实际上无毒的产品。尽管如此，必须考虑水质，血液学和组织学改变来确定体内应用的浓度和策略。