Skip to Content

Can Fish See Red Light?

There is one debate that has been going between fish keepers for decades with both sides of the argument always trying to back up their own points when it comes to if fish can see red light or not.

In the grand scheme of things, there are definitely more important things to worry about but we often see debates going over the ability of fish to see red light in their tanks.

Due to this, we wanted to put our own article online to try and show that there is actually evidence to back up both sides of the argument in different situations.

It is not as clear cut as a yes or not answer and this is why both sides of the debate tend to try and back their arguments as passionately as they do.

We will be covering a number of different questions in this article and you are able to use our table of contents below to skip directly to specific sections of the article quickly.

We will be making a number of points and different stages throughout the article though so it can be a good idea to at least skim all three sections though.

Can Fish See Red Light?

Fish are able to see red light if red light is present meaning that aquarium fish are see any red light around them due to the water being easy for red light to penetrate.

Wild fish in deeper water can struggle with redlight due to there being so little light available as the red light wavelengths tend not to penetrate the water to such depths.

Once deep water fish are bought closer to the surface where red light can penetrate then they are able to see any red light around them as many deep water fish do actually have the ability to see red light if it is around them.

There has been a number of studies done into the ability of fish to see red light with all concluding that the majority of fish species tested are able to see red light.

This is why your fish may scatter if you shine a red light pointer into their tank with all of the other lights off due to perceiving it as a threat. Red light can be deemed as the reflection of any light off anything that is red too and fish are able to quickly and easily identify red food types such as bloodworm.

Although the bloodworm logic is commonly quoted in the debate on if fish can see red light, the vision of the fish only comes into play for the last couple of inches between the fish and the bloodworm, the rest of the distance is usually covered by following the fishes sense of smell.

Can You Use Red Light In Your Aquarium?

You are able to use red light in your aquarium without causing harm to your fish and many aquariums will come with red LEDs fitted as standard.

Due to red light not being considered as harsh as white light you may be able to use red light to observe your skittish or nocturnal fish that tend to hide during white light.

One thing that we would point out is that some algae species will grow at a much faster rate when in red light instead of white light.

This is due to some algae doing much better in the red light spectrum so if you suddenly start to have problems in your tank after starting to use the red light on a regular basis, try switching back to white or another light color.

Snails, shrimps, and amphibians do tend to be fine in red light too so if your aquarium does have a red LED on it then feel free to experiment with it to see how your fish react or as a way to get the tank to fit the look of the rest of your room.

With more and more fish keepers starting to try and match their tank with their smart lights to complete the overall look of the room, red and blue light for aquariums is becoming increasingly popular.

What Does Red Light Do to Fish?

Red light does not harm fish and most species of fish are able to see it so there is no need to worry about using red light around your fish.

In some situations, with some parasites such as velvet (sometimes called gold dust disease), red light can be recommended as the parasite needs white light to survive on your fish.

We have seen some people claim that red head torchers were developed for people who like to go night fishing due to fish not being able to see the light and it acting as a way to catch the fish, unhook them, and then release them.

This is not correct at all and is just a piece of incorrect information that constantly gets handed around on social media.

Red head torches were developed due to the red light wave lengths not traveling as far as other light colors making it ideal for a number of uses. The military, law enforcement, hunters, and construction workers in built up areas at night all have uses for red head torches.


That brings our article going over if fish can see red light or not to an end. We hope that we have been able to help you better understand how both sides of the argument are technically right but when it comes down to it, most fish are able to see red light if they are in a depth of water that red light is able to penetrate too.