Fish can see Red Light?

[SteveMM62Reef]

I got a Red LED Penlight, that was advertised for Night Vision, reading maps, checking for animals at night. It replaces my MiniMag with the Red Lens, that disappeared. Didn’t notice fish could see this light, new light is brighter with a narrower beam. Even backing off, it seems they see the light. I’m Using it for Invert checks at night.

 

[ISpeakForTheSeas]

Yeah, despite common belief to the contrary, only deep sea fish (200 meters deep and deeper) can't see red light - shallow/non-deepwater fish like we get in the hobby can see red light (and some can see UV and Infrared as well):
https://www.nature.com/articles/s41598-021-94355-6

-Some fish (like salmon) and inverts (like mantis shrimp) can see infrared.
https://source.wustl.edu/2015/11/fr... from the open,ability to see infrared light. https://www.science.org/content/article/new-form-vision-discovered#:~:text=Mantis%20shrimp%20eyes%20can%20see,in%20mating%20or%20secret%20signaling&text=When%20it%20comes%20to%20versatile,its%20color%20vision%20tops%20ours.

That said, clownfish can also see UV light,** so it may be rather bright in there for the clown too (it may hurt the clown's eyes if it's bright enough). - Fun fact for anyone interested here, the UV reflectance of clownfish is also related to intraspecific aggression and their social hierarchy.***

**Source:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8511661/ ***Source:
https://academic.oup.com/beheco/article/34/1/19/6782928

 

[i cant think]

Yeah, despite common belief to the contrary, only deep sea fish (200 meters deep and deeper) can't see red light - shallow/non-deepwater fish like we get in the hobby can see red light (and some can see UV and Infrared as well):
https://www.nature.com/articles/s41598-021-94355-6

Sometimes it’s scary knowing what fish can do, we tend to say they’re dumb and such but actually some of them are insanely clever.

 

[VintageReefer]

I do think they can see red light but have reduced vision. I had to catch some fish in my display and was failing miserably and searched the forums and people suggested using red light only.

I set my led to reds only on 5-10% (I forget) and I had both fish caught in a few minutes. They did see my net and acclimation box that I was herding them into, but when I tried with blues on 3-5% they were much more aware and completely avoided the box