Study of Blue LED Light Intensity on Zebra Fish Behaviour in Aquarium

Blue LED lights, peaking at about 470 nanometres, strongly affect how fish act in aquariums. This has big implications for fish farming practices and ensuring good animal welfare. In this research, we explored the effects of different blue light intensities from 10 to 500 lux on social grouping, swimming activity, and stress behaviours in adult zebrafish, a popular model for aquatic studies. The experiment involved 15 groups, each with 12 healthy adult fish, housed in 50 liter tanks. Fish experienced a standard 12 hour light and 12 hour dark cycle over 14 days. We recorded behaviours daily using automated video tracking software. Key measures included shoal cohesion (average distance to the nearest neighbour), overall swimming speed, and thigmotaxis (time spent near tank walls, indicating anxiety). We also monitored opercular beat rates as a direct sign of physiological stress. Findings revealed a clear pattern tied to light strength, but not a simple straight-line response. At low levels (10–50 lux), fish showed 25% tighter grouping and 18% more exploratory swimming than in very dim conditions. This suggests better social bonds and interest in their surroundings. Medium intensities (100–200 lux) maintained steady, natural activity levels with no rise in stress, aligning with typical daily rhythms. High levels above 300 lux triggered anxiety fish clustered very closely, swam slower overall, hugged walls more, and had faster gill beats. Zebrafish have unique eye cells highly sensitive to blue light, which likely disrupts their internal clocks. For aquaculture, we recommend keeping blue LED below 150 lux to prevent behavioural issues, promoting healthier growth and stronger fish. Switching to greenish light around 520 nm at moderate levels could improve conditions further. Future studies should measure clock related genes and test other farmed species to perfect LED lighting strategies.