How do I create dawn and dusk effects?

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One reader asks advice on setting up a lighting system in his tank.

I am in the process of setting up my first freshwater aquarium. My initial thoughts were for a natural planted environment to include a programmable lighting system to create dawn/dusk effects. I want to retain the cover on the tank, to stop fish jumping and to slow evaporation, but this seems to preclude the system I want. If I can physically fit one in below the cover at a suitable distance from the water, then why not? Am I missing something? Please could you advise?

RICHARD PRIESTMAN, VIA EMAIL

Neale responds: It is certainly possible to create dawn and dusk effects, and partly, it will depend on the aquarium you have. At its simplest, you can connect each of the lamps (or LED strips) over your aquarium to separate timers. Have one come on first, then the second a given period of time later, and so on, until full illumination is reached. Do the same thing in reverse, to create a gradual dimming of the tank. 

Obviously, this sort of approach won’t work if your tank has just a single lighting unit that’s either on or off. In any event, switching lamps on and off provides only a crude approximation of dawn and dusk. Your fish won’t be too fussed, and all that matters to them is that they don’t have the lights come on suddenly in a dark room. So long as there’s ambient room lighting before the aquarium lights come on, they’ll be fine.While LED can be dimmed or brightened for special effects, this isn’t the case with traditional fluorescent tubes, which are either on or off. It is possible to buy devices that will dim and brighten LEDs in a controllable manner. However, this may or may not be an option depending on your particular set-up. Most of the Juwel tanks, for example, can be fitted with LEDs even if originally purchased with fluorescent tubes, and Juwel produce a device called the HeliaLux Smart Control that works with the HeliaLux line of LEDs. These aren’t cheap: kitting out the popular Juwel Rio 180, for example, will cost you over £350 for the HeliaLux 1000 LED and Smart Control unit.
But the device does provide an impressive range of features, including dusk and moonlight settings. It’s a WiFi device you control using a computer or smartphone, which makes creating custom lighting effects a lot easier than trying to the same thing with an array of analogue timers and separately wired lamps. 
Doubtless other systems exist for other types of aquaria, and your local retailer may be able to talk you through some of the options. But yes, such systems exist, and while pricey, they do provide an extra dimension to aquarium lighting that adds considerably to their realism.