[nchmi28]

I've read that fish don't see red light, so it is a good way to observe nocturnal fish. I'm in the very early planning phase of a new tank. One of the fish I'm considering is Kuhli Loaches. I'm wondering if I made a cave, with an open side up to the glass, then put a red film over the outside of the glass, if I'd be able to watch them while they were in their cave during the day. Does any one have any input on whether or not this would work?

 

[roadmaster]

Below fifteen feet ,red is near invisible to fish, or so say those who make/sell red fishing line.
Above this depth, I have caught crappie on red jig's when they would not hit any other color I was in possession of that day.
I use a LED light that stretches over my fishing cap to observe the nocturnal meandering's of pleco's,cory's, and loaches.
The light has a couple white LED bulb's with one RED setting which keep's bug's away from your face at night.
It is also excellent for viewing the fish at night in my aquarium's for they are not as startled by the red light as they are with the white bulb's from the fishing light,or the light's over the tank.
I used the light to observe inside the pleco cave's whilst the male's are fanning the egg's, and to keep track of how many day's it took on average for the egg's to hatch and wriggler's to appear inside the cave.
Can find the fishing cap light's at Walmart in sporting good's.

 

[Nordic]

Kuhlis are cool. Used to have quite a few. They are not that shy if there are enough of them around.
But they do enjoy a nice crevice or gap under a rock etc...

 

[nchmi28]

Thanks for the replies. What I'm really trying to figure out is; If I provided a cave with a red window, for me to view them through, would they use the cave? Or would the red light coming in make them look for hiding places elsewhere? If no one has tried this, it might be a thing that I'll just have to try and see if it works.

 

[RyRob]

Red is the shortest visible wave length of light (next is infrared, infra means below, so below red = infrared) that humans can see so red light penetrates the least amount depth in water (besides infrared) around 15-20 ft. The fish seen the red jig because the fish was inches away from it and white light was reflecting red off the jig being perceived by the fish (even if it was a glow jig but light would be used to charge the glow through air instead of reflecting it through water, in the case of glow it's still emitting red light so depth doesn't really take part here, distance from the jig would better fit here) pink is also great for crappie. The white light penetrated the water, no matter the depth, and reflected the red of the jig. Just watch some deep sea extavating/exploration videos, if they turn on a light 2 miles below the surface, you can see the colors of what they are looking at. Light dispersion is relative to the light source. Back to your question, if you were to put the red window in your tank, and shine a light through it, even if the fish is color blind it will still be able to see the intensity of the light, no matter the color because you are diffusing white light through a red filter that is inches(?) away from your critter. The water is nowhere deep enough to for the red light to dissipate. But, using a red light would still be way less stressful than shining a bright white light in there. I use a 50 lumen white led flashlight from Wal-Mart for afterhour viewing, it's not bright enough to wake up my tiger barbs and I can still examine my tank pretty well. In your case, I would skip the red screen and just use a red light. I bought an Ozark Trail headlamp for ice fishing that has a 2-intensity spot light and a 2-intensity flood light that has a "red" mode. The red is to keep our eyes more adjusted to our night vision. It also keeps bugs out of your face and you are less visible (supposedly) to animals but in our situations of fish keeping, unless your white light is super bright, I don't think it really matters much. I'm far from an expert and I'm sure others have better info than I but these are the conclusions I've experienced. Cool topic to experiment with.

 

[nchmi28]

Red is the shortest visible wave length of light (next is infrared, infra means below, so below red = infrared) that humans can see so red light penetrates the least amount depth in water (besides infrared) around 15-20 ft. The fish seen the red jig because the fish was inches away from it and white light was reflecting red off the jig being perceived by the fish (even if it was a glow jig but light would be used to charge the glow through air instead of reflecting it through water, in the case of glow it's still emitting red light so depth doesn't really take part here, distance from the jig would better fit here) pink is also great for crappie. The white light penetrated the water, no matter the depth, and reflected the red of the jig. Just watch some deep sea extavating/exploration videos, if they turn on a light 2 miles below the surface, you can see the colors of what they are looking at. Light dispersion is relative to the light source. Back to your question, if you were to put the red window in your tank, and shine a light through it, even if the fish is color blind it will still be able to see the intensity of the light, no matter the color because you are diffusing white light through a red filter that is inches(?) away from your critter. The water is nowhere deep enough to for the red light to dissipate. But, using a red light would still be way less stressful than shining a bright white light in there. I use a 50 lumen white led flashlight from Wal-Mart for afterhour viewing, it's not bright enough to wake up my tiger barbs and I can still examine my tank pretty well. In your case, I would skip the red screen and just use a red light. I bought an Ozark Trail headlamp for ice fishing that has a 2-intensity spot light and a 2-intensity flood light that has a "red" mode. The red is to keep our eyes more adjusted to our night vision. It also keeps bugs out of your face and you are less visible (supposedly) to animals but in our situations of fish keeping, unless your white light is super bright, I don't think it really matters much. I'm far from an expert and I'm sure others have better info than I but these are the conclusions I've experienced. Cool topic to experiment with.

Thanks for the awesome explanation. The experiment I'm going to try is, having one edge of an under gravel filter pushed up to the tank glass.

I'm going to run red transparent tape along the outside to create the window. So that hopefully when I shine a light in to peak at the kuhli loaches, I won't disturb them. I've started a journal for this tank, if your interested in seeing how it goes.

 

[Nordic]

Never mind the fish... your plants may not enjoy the red light.
Many plants have their dark cycle severely disturbed by even small flashes of red light.

 

[nchmi28]

Never mind the fish... your plants may not enjoy the red light.
Many plants have their dark cycle severely disturbed by even small flashes of red light.

The only place where the red light will be reaching is inside the underground filter, there shouldn't be any plants down there.