Looking For Advice On Led Lighting

Please don't run lights all the time, it would seriously stress the fish. They need a period of total darkness during every 24 hours. The lights should be on for the same period of the day, every day. It takes up to an hour for a fish to adjust to the lights going on and off. If the lights are on at the same time every day, they get used to this routine and their eyes begin to change in advance of the on or off.

This is from an article written by Byron Hoskins

The health of fish is closely connected to the intensity of the overhead light, various types of light, and sudden changes from dark to light or light to dark. To understand this, we must know something about the fish’s physiology. The primary receptor of light is the eye, but other body cells are also sensitive to light.


Fish eyes are not much different from those of other vertebrates including humans. Our eyes share a cornea, an iris, a lens, a pupil, and a retina. The latter contains rods which allow us to see in dim light and cones which perceive colours; while mammals (like us) have two types of cones, fish have three—one for each of the colours red, green and blue. These connect to nerve cells which transmit images to the brain, and the optic lobe is the largest part of the fish’s brain.

These cells are very delicate; humans have pupils that expand or contract to alter the amount of light entering the eye and eyelids, both of which help to prevent damage occurring due to bright light. Fish (with very few exceptions such as some shark species) do not have eyelids, and in most species their pupils are fixed and cannot alter. In bright light, the rods retract into the retina and the cones approach the surface; in dim light the opposite occurs. But unlike our pupils that change very quickly, this process in fish takes time. Scientific studies on salmon have shown that it takes half an hour for the eye to adjust to bright light, and an hour to adjust to dim light. This is why the aquarist should wait at least 30 minutes after the tank lights come on before feeding or performing a water change or other tank maintenance; this allows the fish to adjust to the light difference.

The Day/Night Cycle

Most animals have an internal body clock, called a circadian rhythm, which is modified by the light/dark cycle every 24 hours. This is the explanation for jet-lag in humans when time zones are crossed—our circadian rhythm is unbalanced and has to reset itself, which it does according to periods of light and dark. Our eyes play a primary role in this, but many of our body cells have some reaction to light levels. In fish this light sensitivity in their cells is very high.

Previously I mentioned that the rods and cones in the eye shift according to the changes in light. This process is also anticipated according to the time of day; the fish “expects” dawn and dusk, and the eyes will automatically begin to adjust accordingly. This is due to the circadian rhythm.

This is one reason why during each 24 hours a regular period of light/dark—ensuring there are several hours of complete darkness—is essential for the fish. In the tropics, day and night is equal for all 365 days a year, with approximately ten to twelve hours each of daylight and complete darkness, separated by fairly brief periods of dawn or dusk. The period of daylight produced by direct tank lighting can be shorter; and the period of total darkness can be somewhat shorter or longer—but there must be several hours of complete darkness in the aquarium. The dusk and dawn periods will appear to be stretched out, but that causes no problems for the fish. It is the bright overhead light that is the concern, along with having a suitable period of total darkness. And the "day" period when the tank lights are on should be one continuous period, not sporadic, and it should be the same every 24 hours or it will impact the circadian rhythm causing more stress.
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No, fish need a period of total darkness. Companies may make lights advertised for leaving on all night but we all know that just because someone makes something doesn't mean it is a good idea.

I'm afraid I have to say no again. The lights should be on at exactly the same time every day.

it should be the same every 24 hours or it will impact the circadian rhythm causing more stress.

As an example, I have 3 lights on my tank, two large LEDs the width of the tank and a tiny blue LED.
One of the large LEDs switches in at 11.30 am while the room is in daylight. The second switches on at 12.00. The first large one switches off at 18.30. The small blue LED switches on at 18.55, and the second large LED switches off at 1900. The tank is in the dining room which by now is dark in winter. The blue LED stays on till 19.30, and its sole purpose is so that the fish are not suddenly plunged from a bright LED into total darkness.
In summer I do not use the blue LED as the room is still in daylight when the large LEDs turn off, and the room gets slowly darker during the evening.
I don't alter these times at all; the only time they vary from the fish's viewpoint is when we change from summer time to winter time, then back to summer time.

My tank isn't nearly as big as yours so I have no idea which lights would fit your tank, I'm afraid. They do make the ones I have in 150 cm long. The next size down is 120 cm. https://www.fish-fish-fish.com/superfish-retrofit-bright-white-led-150cm-27839-p.asp

just bought the same one sue has, will see what it's like