Generally if the fittings are of a good quality, you just need to make sure that you get new bulbs, or ask how many hours old the current bulbs are. The longer the running time the longer the wave lengths become, meaning a new bulbs run at around 400nm, this is at the blue end of the spectrum, as the bulb ages, the wavelengths get longer or move towards the red area, not that you would notice, unless you had an old and new bulb side by side, then it is noticeable. The thing is, is blue light or the lower end of the spectrum penetrates deeper into the water column, hence the reason water appears blue and not red to the naked eye.
