Do Aquarium Fish Need Light in The Tank at Night

By Eddie Waithaka @aquariawise

Do Aquarium Fish Need Light in The Tank at Night

Light and aquariums can be confusing since an optimal balance is hard to catch, more so when keeping fish in a planted tank and with species from different wild environments.

While most tropical fish will need light to feed and do other fishy things, long light periods without a few hours of darkness will stress your fish.

Too much light in the tank will also boost algae growth, something you do not want.

Hence, anywhere from 8 to 10 hours of light will serve in an average tropical tank. The light cycle should mimic normal daylight and dark hours.

So, does this mean your fish tank should always be dark at night?

Well, not exacty!

Yes, most tropical aquarium fish will rest after a period of being active, and the time for sleep mostly coincides with nighttime, but some loaches, plecos, and catfish prefer to feed during these hours.

You may also want to enjoy the tranquility of your fish tank at night (after a long day of work), and turning the lights off may not be feasible.

As such, the best approach is to allow your fish some hours with the lights off for rest, preferably at night. If you have nocturnal fish, you can leave the lights on a while longer for them to feed or use a calm blue light during these hours.

The blue light will also let you enjoy your fish (including skittish finnies that rarely venture out during the day) at night but still allow them to rest.

Fish do not need light in the tank at night, but a calm blue light will let you sight and enjoy your finnies and may even assist nocturnal species feed with ease.

Do Aquarium Fish Need A Night Light

A night light in your fish tank is not so much for your fish but your viewing benefit. Most of your fish will rest (or sleep) at night, reserve to a few nocturnal loaches and critters, hence don’t need the light.

Typically, even nocturnal finnies do not need the light, though it does help them swim across the tank and sift the substrate with ease. Their nocturnal instincts and ability should help them feed even without light.

A calm blue light is recommended for use in an aquarium at night because it will illuminate it enough for you to sight your fish and remain chill for your fish to sleep.

Algae will also not thrive under the blue light as it does under a full-spectrum light meaning you can use it for an extended period.

Convinently, you also don’t need to buy a separate blue aquarium light for your fish tank. Most fixtures will come with a moonlight setting which is just a fancy name for the night light.

As you may already know by now, I’m a sucker for this Nicrew classic LED gen-2 aquarium light. It has an inline controller that allows you to operate the white and blue light together or independently and adjust the intensity and spectrum as you wish.

The amount of control makes the light ideal for freshwater and saltwater fish-only and low-light aquarium plants and is dimmable to moonlight settings for use at night.

Should I Leave My Fish Light on All Night

Now that we’ve established your fish will be fine even without light at night in the fish tank, there is no reason or benefit for leaving your aquarium light on all night long.

Even if you need to enjoy watching your finnies after work, a blue light will suffice, and remember to turn it off before you go to bed.

It is Ok for fish to be in the dark. A period of darkness allows your finnies to sleep, plus leaving the light on all night could cause algae to grow exponentially and take over your tank.

You’ll also want to dim your aquarium room ambient lighting because too much of it will encourage algae growth even when not intentionally directed into the tank.

One other reason you do not want your aquarium light to run all night long (away from allowing your fish some time to rest and to discourage algae growth) is for the sake of your skittish and nocturnal finnies and critters.

Fish like kuhli loaches and bristlenose pleco barely venture out during the day, and the time they can swim freely and feed is at night when the lights are off or dimmed.

What Color Light Do Fish Like at Night

I’ve already mentioned this a couple of times, but it does not hurt to repeat. Your fish do not have a light preference at night, or even during the day), a bulb’s color and intensity is mostly for aesthetics and maybe if you have plants in your aquarium.

When considering your fish, the only important aspect is the number of light hours (and darkness) you allow in your fish tank.

Are the duration even, and does your fish get enough dark time to rest?

Now, aesthetically, I would say a blue (moonlight) bulb or setting in your aquarium at night best serve the fish resting part and your viewing, but this changes when considering a planted tank.

Blue light is perhaps not needed that much by plants, plus you need to consider a lot more (spectrum, intensity, and what have you), but it is by far the best option at night.

It’ll bring out your fish colors and give corals in reef tanks a pretty interesting look.

A white or daylight bulb offers the best lighting in terms of brightness and allows the best visuals to see what is in a tank. It will also highlight bold colors on fish, coral, and red plants, but it’s not useable at night.

A brilliant magenta hue dramatically enhances green, pink, blues, and red colors on freshwater fish and plants but won’t help your plant’s growth per se.

It’s also not the ideal light for use at night either.

Thats all for this post.

Happy fish keeping🐠🐟🐡.

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