Cobalt Blue Goby

The cobalt blue goby reaches about 5 cm standard length and is a specialised biofilm grazer from clear, fast-flowing coastal streams across Indonesia, New Guinea, and the Solomon Islands. Males develop a vivid blue body colour that fades in subordinates or stressed individuals. The aquarium should measure at least 60 by 30 cm (about 54 L) with strong flow, high oxygenation, and a mature biofilm coating the rocks. Fit a secure cover, as these gobies can climb aquarium glass. Temperature of 22–28 °C and pH 6.5–7.5 suit it, but the upper end of the temperature range needs extra surface agitation to maintain dissolved oxygen. They are peaceful and can be kept with small danios or rasboras in the upper levels; keep one male with two or more females to spread male attention. Algae-covered rocks are essential — sinking dried foods and occasional bloodworm are accepted but should not replace the biofilm that their long gut is designed to process.