**Background:** Aquaculture is increasingly popular, but artificial breeding of aquarium fish faces challenges from harmful water substances and fungal infections. Humic acids (HA) from fossil minerals like alginite have shown beneficial properties including detoxification, immune stimulation, and improved survival in adult fish, but their effects on eggs and fry were not well studied. This study aimed to evaluate the effect of different HA concentrations on mortality, growth, and water quality during artificial incubation of roes and development of fry in the mouthbrooding African cichlid Labidochromis caeruleus.
**Methods:** Eight adult females and four males (2 years old, 11–13 cm) were kept in 240 L aquariums at 24 °C, hardness >15 °dGH, pH 8.0. Females with roes in their buccal cavities were caught and roes were released by rinsing the buccal cavity with a syringe. Roes were randomly assigned to 4 groups of 40 (2 replicates of 20 each): Group 1 (1% HA), Group 2 (5% HA), Group 3 (10% HA), and a control group (no HA). HA was extracted from gamma-irradiated alginite using an alkaline Na₄P₂O₇ solution, yielding a leachate with 72% humic acids. Roes were incubated for 5–7 days, then fry were transferred to 10 L aquariums with matching HA concentrations, heated to 26 °C. Mortality was recorded on day 5 and day 30. Body length (from gills to tail beginning) was measured in histological sections from 12 formalin-fixed fry per group using ImageJ. Yolk sac absorption was assessed visually on days 22, 24, 26, 28, and 30. Water temperature, pH, general hardness, nitrite, and nitrate were measured every 5 days using Sera Quick tests. Statistical analysis used ANOVA at α = 0.05.
**Key Results:** On day 5 (after hatching), mortality was 30% in controls, 17.5% in the 1% HA group, and 5% in both the 5% and 10% HA groups. By day 30, mortality was 40% in controls, 20.0% in the 1% HA group, 7.5% in the 5% HA group, and 10.0% in the 10% HA group. ANOVA confirmed that 5% and 10% HA concentrations had a statistically significant effect on survival. Fry body length was greater in the 5% and 10% HA groups compared to controls by the end of the 30-day period. Yolk sac resorption was accelerated in all HA-treated groups; notably, between days 26 and 28, 90% of fry in the 5% and 10% HA groups had absorbed their yolk sacs compared to 50% in controls. Water quality analysis showed that HA reduced nitrite and nitrate levels in a concentration-dependent manner. The control group reached nitrate concentrations of 100 mg/L, which likely contributed to the 40% mortality. HA also reduced pH and water hardness, with 5% and 10% concentrations effectively stabilizing these parameters. The control group had pH values in the alkaline range, increasing mold risk for roes and fry.
**Clinical Implications:** The addition of humic acids at 5% and 10% concentrations significantly improved survival and growth of African cichlid fry during artificial breeding by stabilizing water chemistry—reducing toxic nitrites and nitrates, lowering pH, and decreasing water hardness. These effects reduced fungal growth and created a more stable environment. The accelerated yolk sac resorption and increased body length suggest HA may have direct physiological benefits beyond water quality improvement. This practical, low-cost intervention could enable less experienced aquarists to successfully breed species that are difficult to rear artificially. The study is limited by its small scale, single species focus, and lack of blinding or randomization details. Further research should examine optimal dosing, mechanisms of action, and applicability to other fish species and larger-scale aquaculture operations.