Is the UV lamp useful for decorative freshwater (aquarium) fishes or may it be rather dangerous instead?

As far as I am aware the Sun causes fishes' coloration to saturate, and although the UV lamp only resembles sunlight, it is still supposed to provide such effect.

And on the other hand, the irradiation is potentially harmful to people during protracted exposure; can it also be as dangerous to the fish?

  • Are you trying to ask if fish can get sunburn? Dec 5, 2016 at 13:38
  • @JamesJenkins I am asking is it dangerous for them in any manner or is it as helpful as it is for people and will it colorify them as if they are exposed to sunlight.
    – Malina
    Dec 5, 2016 at 16:07
  • 1
    Can you explain what type of UV light you're specifically asking about? There are several types and spectrums of UV bulbs, the 2 common types of UV are A and B. Strong UV A will sterilize water by destroying the bacteria, viruses, and even algaes and macro-planktons, these are only commonly used for sterilizing applications. If you just mean a UV bulb like a plant grow bulb, which is mostly a UV B, it likely will cause algae problems unless you setup a planted tank. I've never seen a fish change color permanently due to increased pigmentation, like a human, specifically because of a bulb.
    – Jestep
    Jan 27, 2017 at 14:55
  • @Jestep I have only a medical quartz lamp. A bit more than just a bulb :)
    – Malina
    Aug 9, 2018 at 0:25
  • Please never use germicidal quartz-glass lamps for illuminating aquarium nor anywhere else near living things that are dear to you; these lamps emit UVC which could cause eye damage including permanent blindness, painful and blistering skin burns and cancer. On top of that, UVC ionizes oxygen in the air, which generates ozone - an unstable and highly toxic gas that damages respiratory, cardiovascular and central nervous system.
    – lila
    Apr 2, 2021 at 23:27

2 Answers 2


The answer to your question is yes and no.

If you are using UVA light (black light) then this is safe for your fish; most of the light sources used on fish tanks do emit these wavelengths to some degree, but the black light sources are coated with a material that filters out the other wavelengths from red to blue light so it radiates only near ultraviolet and infrared light (heat).

The dangerous types of ultraviolet light are UVB and UVC; UVB is what gives you a tan or a sunburn, while UVC is the most dangerous type of ultraviolet light - this is used to kill bacteria and algae in water and to sterilize surgical equipment, among lots of other uses.

UVC radiated from the Sun is stopped by the atmosphere so it does not reach the ground, but it can be measured in Antarctica due to the ozone hole there.

More information could be found in this Wikipedia article about ultraviolet light.

enter image description here

Near UV = UVA.

Middle UV = UVB.

Far UV = UVC.

  • I thought UVC is absorbed by the ground rather than being stopped by the atmosphere.
    – Malina
    Aug 9, 2018 at 0:23
  • 1
    @Malina i added a link to better explain the different types of ultraviolet light. Aug 11, 2018 at 5:20

Nothing can be compared to natural sunlight.

I recently moved my fish from artificial lighting to my balcony - open to air, sunlight and without a lid.

The difference was evident within two weeks. At first, my fish were scared of the open. Now, their colours are significantly more saturated. The fish have also become incredibly active (and hence hungry). They also know when to dive down into the water when crows arrive.

My nocturnal aquarium snails seem to be happy too.

  • 6
    Does not scientifically answers the question, but it is interesting reading besides the fact it is also useful information.
    – Malina
    Dec 8, 2016 at 22:15
  • Not an answer to the question.
    – lila
    Jun 6, 2021 at 23:49

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