all but my 10 gallon are on timers. I'm not sure if I have one for it, but I probably should get it on one
Why is a tank's lights being on a timer so important?
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To answer your original question...it matters a great deal on three fronts, plants, algae and fish. I'm doubtful some bother to read linked articles, so I will cite from mine on this subject of why light is a crucial factor in fish health, and those interestd can read the linked article.
First, a regular photoperiod can prevent all problem algae once you have the balance for the plants. Second, it affects plants because light intensity drives photosynthesis, and to photosynthesize plants need the 17 necessary nutrients in balance. This is the algae issue again as well. But plants are more adaptable in this, which is why as far as the plants are concerned the "siesta" lighting approach can work. But it is the fish that suffer most.
The health of aquarium fish is closely connected to the intensity of the overhead light, various types of light, and changes (both sudden and gradual) 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. Pencilfish in the genus Nannostomus have a diurnal patterning--at night the lateral lines break up into dashes, and the fish pales. This has been noted to occur even in blind fish, which shows that it is not sight that tells the fish it is getting dark, but the increase in darkness probably coupled with the circadian rhythm that sets in motion the natural response of the fish to darkness.
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 tropical habitats of the majority of our aquarium fish, day and night are basically equal for all 365 days a year. The period of "daylight" produced by direct tank lighting can be shorter--though it must be continuous, not broken up; and the period of total darkness can be somewhat shorter or longer provided there are several continuous hours of complete darkness in and around 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.
First, a regular photoperiod can prevent all problem algae once you have the balance for the plants. Second, it affects plants because light intensity drives photosynthesis, and to photosynthesize plants need the 17 necessary nutrients in balance. This is the algae issue again as well. But plants are more adaptable in this, which is why as far as the plants are concerned the "siesta" lighting approach can work. But it is the fish that suffer most.
The health of aquarium fish is closely connected to the intensity of the overhead light, various types of light, and changes (both sudden and gradual) 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. Pencilfish in the genus Nannostomus have a diurnal patterning--at night the lateral lines break up into dashes, and the fish pales. This has been noted to occur even in blind fish, which shows that it is not sight that tells the fish it is getting dark, but the increase in darkness probably coupled with the circadian rhythm that sets in motion the natural response of the fish to darkness.
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 tropical habitats of the majority of our aquarium fish, day and night are basically equal for all 365 days a year. The period of "daylight" produced by direct tank lighting can be shorter--though it must be continuous, not broken up; and the period of total darkness can be somewhat shorter or longer provided there are several continuous hours of complete darkness in and around 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.
@Byron - that was a very useful and serious explanation - much appreciated.
I picked up some Beckford's pencils and emperor tetras not long ago, and today is their second day in their post QT tank. This morning, the lights around them came on, and their bodies had their night-time colours. I thought the room lighting would provide a transition, but when their tank's light clicked on, they were quite discombobulated, and were still in their pale colours. About 10 minutes later, they had adjusted.
I'm assuming this is a side effect of their new tank, and in a few days, they'll have the rhythm down - ambient lights come on, and a while later, bright light appears. But going from room lighting to the tank light distressed them, for certain.
I should have put 2 and 2 together before I said it was convenience. If you are a creature of habit, manually operating lights is fine. If not, or if you have a job that makes to change schedules, a light timer is clearly more than simplicity.
I picked up some Beckford's pencils and emperor tetras not long ago, and today is their second day in their post QT tank. This morning, the lights around them came on, and their bodies had their night-time colours. I thought the room lighting would provide a transition, but when their tank's light clicked on, they were quite discombobulated, and were still in their pale colours. About 10 minutes later, they had adjusted.
I'm assuming this is a side effect of their new tank, and in a few days, they'll have the rhythm down - ambient lights come on, and a while later, bright light appears. But going from room lighting to the tank light distressed them, for certain.
I should have put 2 and 2 together before I said it was convenience. If you are a creature of habit, manually operating lights is fine. If not, or if you have a job that makes to change schedules, a light timer is clearly more than simplicity.
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I appreciate all the input and found it useful. I DO have a timer that is not in use and may apply but I would need to also use an extension cord as the timer only has one outlet and my hood lights use 2 AC adapters. No idea as to why the lights take 2 plugs but it is what it is.
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