Effect of tank colour on Eurasian perch (Perca fluviatilis L.) farming in a recirculating system

The aim of the study was to determine the influence of tank colour on growth performance of Eurasian perch (Perca fluviatilis L.) farmed in a recirculating aquaculture system (RAS). A total of 96 Eurasian perch (Perca fluviatilis L.) with live weight of 10.38–17.30 g were distributed in four groups. The fish were reared in plastic tanks of different colour (black, red, green and white) with effective volume of 0.05 m3, part of a RAS. An 800 lx, 12 hours light/12 hours dark light regimen was provided in the facility. Perches received extruded rainbow trout feed „Aqua garant UNI“ with pellet size 2 mm ad libitum three times a day. The experiment duration was 30 days. During the experiment, the RAS water chemical parameters were maintained within the optimum ranges for the species. The highest average individual weight gain was found in fish cultured in green tanks (7.17±0.55 g, P≤0.05), which was by 20.50%, 21.06% and 22.18% higher than those cultured in black, red and white tanks. The highest food intake was registered in the perch group farmed in green tanks - 154 g, which was 11.04%, 14.94% and 20.78% higher than the same parameter in black, red and white tanks, respectively. FCR was the best (P≤0.05) in fish from green tanks: 1.07±0.05, and by 6.54%, 10.28% and 7.47% higher than those from black, red and white tanks, respectively. The survival rate of perch was the highest in the black tanks - 87.50%, by 9.52% higher than that of fish in the red and white tanks, and by 4.77% higher than that of fish in the green tanks. The greatest SGR was observed in the fish from the green tanks 11.95±1.05, which exceeded significantly (P≤0.05) SGR of fish reared in the black, red and white tanks by 20.50%, 21.09% and 22.18%, respectively. Our observations showed that Eurasian perch in green tanks were calm, resulting in very good performance in terms of feed intake, FCR, SGR and weight gain. Also, fish had an intensive green colour, similar to that of wild fish from this species.