If there are no live plants in the aquarium the fish will probably be ok with the lights out.
Fish tank light off for a week.
In addition aquarium fish can usually tolerate a week without food.
Improper lighting can make your fish lethargic or ill and fish such as goldfish will lose their color or their appetite when stress rears its ugly scales.
If you re keeping freshwater plants or saltwater corals in a reef tank or macro algae in your refugium you really should have a light timer anyway so that your plants and corals receive adequate amounts of aquarium light.
If you have live freshwater plants in your tank or saltwater corals you re probably already doing this in order to provide the light spectrum they need for healthy growth.
Leaving the light on too much can cause an overgrowth of algae in the tank and it will also cause the fish to stay active longer and require more food.
Leaving the light on can cause stress to fish as they need a period of darkness to sleep.
The aquarium lighting can easily be turned on and off automatically using an aquarium light timer.
Leaving it on would be a fire hazard causes algae growth and i ve found that on a hot day the light can.
Other problems from light.
I wouldn t even worry about getting a timer.
Fish don t need a light to live.
So the short answer is no do not leave your lights on.
They may be less active and will thus create smaller quantities of ammonia.
The standard requirement for aquarium lighting for fish is usually 12 hours of light each day.
Too much sunlight can heat the water of your tank up to uncomfortable or dangerous levels and it can also increase the amount of algae which can cause bacterial infections.
The fish do not need light and it is best that your turn it off during the night.
A good way of ensuring that your fish can continue to go about their daily routine is by using a timer on your aquarium lights.
Either leave the light off or put it on a timer so that it shuts off overnight and turns back on in the daytime.
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