I have installed a UV lamp in my aquarium and had it on for 12 hours. After that my flowerhorn fish seems to turn pale in colour and his eyes seem to have turned blind. How can I cure my fish? Is the blindness permanent? Please help.

  • 2
    Hi welcome to Pets, UV lamps are never intended to be installed in the aquarium in a way that their output radiates at the animals, the only intended use is if the lamp is to be hidden and embedded inside the UV sterilizer, could you include some details about this lamp? What type of UV is this, is that a germicidal UV-C lamp? Does it look like a fluorescent lightbulb, but with transparent glass?
    – lila
    Jan 18, 2021 at 1:17

1 Answer 1


My recommendations

I would highly recommend turning off the UV lamp and replacing it with a LED light that is on for the daylight hours. In nature, the atmosphere cuts most of UV light and gamma radiation that is hurtful to animals.

The explanation

The issue of blindness is I’m sorry to say is incurable. The UV light has already damaged the fish’s eyes so it cannot be undone. I am very sorry for your flower horn fish.

In general, for any creature, UV light is harmful for the eyes, even for humans (this is why humans also shouldn’t look at UV light directly, same goes for the sun).


The fish’s blind eyes are incurable and that UV light is not needed but LED lights are needed. Only have lights on when outside is bright.

  • 1
    Could you please add an explanation why an LED light is needed? Could it be any LED light or should it have a certain wave length / light spectrum? Any comprehensible explanation or link to an external site is enough, I just want to avoid advice that boils down to "Trust me. Do this because I said so".
    – Elmy
    Jan 18, 2021 at 7:49
  • 1
    Usually red lights are better for plants as they give the spectrum needed to grow. UV lights are to go inside filters as another filtering system. Jan 18, 2021 at 12:12
  • All animals need light or else they will get vitamin B deficiency. thesprucepets.com/led-lighting-1381056 Jan 19, 2021 at 1:50
  • I think what you meant was vitamin D instead of B? It is true that vitamin D could be only synthesized via photochemical process, but absence of light doesn't necessarily mean D deficiency because this vitamin could also be obtained from diet - by eating those organisms who synthesize it, instead of producing it yourself. Also, a large variety of animals actually do live their entire lives practically without ever being exposed to any light. ...
    – lila
    Jan 19, 2021 at 2:27
  • ... What is more, "normal" LEDs don't even emit that part of light spectrum (UV-B) that is required for the synthesis of vitamin D.
    – lila
    Jan 19, 2021 at 2:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.