Lighting

The tank design and the lighting are important as it is desirable to be able to view the fish from the side rather than from above. The tank should be positioned at a height which permits the fish to be viewed at eye level while the observer is either seated or standing. The most effective placing of lighting for an aquarium is above the front glass. Lighting provides illumination but many times it overilluminates certain aspects in an aquarium such as the aquarium walls.

Rainbowfishes differ in their sensitivity to light and to the colour of the background. For example, in species adapted to dark surroundings, bright colours will induce stress. Background colour should mimic the natural environment of the species. In general, they are more relaxed in dark coloured tanks at lower light intensity. It is important to attain a balance between the darkness of the background and the level of light intensity for the benefit of the fish and the requirements of the observer. Problems of the fish reacting to the observer are a function of the inherent boldness or timidity of the species and the light intensity. This can be minimised or eliminated by maintaining the room in darkness relative to the interior of the tank. Red-light lamps can be installed in fishrooms that will allow the hobbyist to perform tasks at night time while the fish are ‘sleeping’.

Several factors including water depth and water clarity affect the colour and intensity of light in aquarium systems. Fluorescent lighting is the most commonly used form in aquaria. Generally, an intensity of 10,000–25,000 lux of full spectrum lighting over the water surface can be used. A colour temperature of 5000–7000 kelvin and peak wave length range of 475–650 nanometre at proper intensity will provide good quality lighting.

Photoperiod is important and requirements vary among species. Although most species do well with a cycle of 12 hours of light and 12 hours of darkness, 8–10 hours of light is generally adequate for most fish, while 12–14 hours can be used for some tropical species. This dusk to dawn system can be set up with a timer that turns a low light on and off for 30 minutes preceding and following the main tank lights. Light (excessive or rapid changes in intensity) should be minimised. Rainbowfishes will often dash frantically about the aquarium injuring themselves in response to normally harmless stimuli such as turning on the fishtank light in a dark room.