Like most living organisms, fish need a source of light to live. However, this doesn’t necessarily mean they need an LED light source for every minute of every day. 

It mostly depends on the type of fish you have, the amount of light in the room without an LED light source, and whether or not you have aquatic plants. 

If you’re looking to get some new fish friends and wondering about whether buying an LED lamp is a waste of money, or if your LED lamp has broken unexpectedly, you’re probably wondering if fish actually need light. 

Luckily for you, we’ve got all the answers you need. 

The short answer

Aquarium fish do need a type of light source to help them determine whether it’s day or night. The circadian rhythm is responded to by most living organisms in the world, and fish are no exception.

Providing a bright light 24/7 will confuse and disorientate the fish as they prepare for a relaxing swim or sleep in the night. 

Some LED light systems come with automatic or adjustable settings that emulate the natural light and dark of day and night. Not only do these make the aquarium look atmospheric for human satisfaction, but it is calming and fits the natural circadian rhythm for the fish. 

However, in most cases, natural light from a window or room light will suffice for fish. This is much cheaper than buying an LED light system and still provides the fish with enough light.

Fish still need a cycle of day and night, so you’ll have to install a light system that emulates this on an automatic timer. 

Do Fish Need Light

Why do fish need light?

Not only do fish need to follow a natural circadian rhythm, but they also need light for health reasons. Fish who live in aquariums with a lack of light source can become lethargic and lose color.

Not only this, but limited light will weaken their immune system and increase their chances of catching and spreading diseases. 

Like humans and other living organisms, without light, fish will become weak and sad. Fish owners should prioritize the happiness of their scaly friends, so an adequate light source is vital for their wellbeing and health. 

Do fish need light at night? 

Darkness is great for fish at night because it helps the flow of the circadian rhythm. Fish need to sleep and rest, which can not be easily done with a light blaring down at them. 

However, as some fish like to swim at night to find a new spot to enjoy the atmospheric setting, most aquarium owners will opt for an LED light system that comes with an automatic night light setting. This is a dim blue light that emulates nighttime without plunging the fish into complete darkness. 

If your fish are in a basement or a room without windows or a light source, it’s not recommended to leave your fish in complete darkness as this can disorientate them.

You should invest in a small light in the room (or an LED blue light above the tank) to provide the fish with a small amount of light to emulate the moon’s rays. 

Leaving a light source on all day and night is a surefire way to increase your electricity bills, which isn’t ideal. Not only this, but keeping a light on over a fish tank will promote algae growth.

Whilst algae aren’t toxic to fish, they will grow rapidly and will make cleaning the tank even more frequent and tougher. It also looks pretty gross. 

How long an aquarium light should be on for

Like the natural life cycle that we are all used to, an aquarium light (or other light sources) should be on for 12 hours and off for 12 hours.

Keep in mind it should only be off if there is another source of dim light to prevent the fish from plunging into darkness, so you can keep an LED light system on at its darkest blue light setting for 12 hours alternatively. 

However, algae love light. You shouldn’t keep an aquarium light on for 12 hours without variation, as this will cause algae to grow rapidly.

Instead, make sure you find a light system that has an automatic setting that dims the lights throughout the day to prevent algae growth. 

We recommend keeping the light on during the day for 8 hours and then turning it off. The fish can survive without a few hours of bright light.

See if there is any algae growth, and each week you can increase the time the light is on by an hour. It all depends on the tank, so you can figure out what works best for you. 

Aquatic Plants

Aquatic plants, like most other plants, need a light source to survive. Not every aquarium owner will have real aquatic plants, so the fake ones will not require a light source, but the real ones definitely do. 

Fish love aquatic plants as it emulates the most natural environment for them. These plants require light to photosynthesize, which will help them grow properly. If they grow too much, you can always prune them. 

Colored Light

It’s not clear whether fish enjoy colored lights or not. Of course, we doubt they’re going to want a disco setting of multicolored lights, but that’s not to say they shouldn’t get any color at all. 

Blue LED lights are ideal for aquariums at night as the gentle blue hue emulates the color of natural water from the moon at night, which can be comforting for the fish. 

As for daylight, you should probably stick to white light. You might be able to mix this light with a gentle color, say purple or green, but the color should be as close to daylight as possible.

The last thing you want to do is disrupt your fish by causing stress from different colored lights, which might have varying temperatures which can alter the pH balance in the tank.