Can fish see red light?

[Togliat]

I was checking my CO2 and air-stone timers early this morning.
Rather than turn on the lights, I decided to try using a flashlight with a red lens (the type you might uses in the field for covertly reading maps or hunting deer, who don't see red...

The fish seemed completely oblivious and failed to react at all.

Do you guys know if fish can see red light? Might this be a way to observe your tank at night without stressing the fish?
(I also have blue LEDs on a timer but they eventually go off, allowing for increased darkness for a few hours).

I am pretty sure that if I flipped on the room lights or used a flashlight with a regular lens, the fish would react...

Just wondering, thanks.

 

[clay16]

A well trusted lfs owner has told me to use a red light at night if I wanted to see " nocturnal life". Never tried yet though lol

 

[Gubernaculum86]

I think most fish can't see red light because that is the first light absorbed by the water and doesn't really penetrate past the first 15-20 ft of the water column. In fact a lot of deep sea fish are red but look black because there is no red light down there