How do fish sleep?

[Jason01]

Well, just to see, and possibly start an argument, I just tried looking at my fish in my 29 gal. tank. I first used the red filter on my light. I moved it around my school of harlequins, and they didn't bat an eye. Just kinda stayed in the same spot. My ghost shrimp, tried to get out of the light when I would spot light them. They(the shrimp) are probably more aware of the light than the fish.

Doesn't end there folks!

I then removed the filter, so the glaring 2 watt LED lit up my school of harlequins like a spot light. They were gone before I could count to 3.

The shrimp otoh, didn't seem to mind being blinded. It might have something to do with the color of the light, as the LED is blueish(it might be more in the harlequins color range, and less in the shrimps).

I would venture to guess that if you want to look at your fish with a red light, go for it! BTW, my tank has a lot of plants in it, and the red light makes it look awful eerie....That and my platies seem to become color less in the red light. Kinda like a non-reflective body. weird!

 

[Debra Mark]

Our clown loaches also like to lie on the bottom - when we first saw this, we thought they had all died! Our Pacu has a favorite spot that he goes to when he wants to rest, facing away from the front glass and in a stream of water from a return line. When the Tin Foil Barbs "sleep", the will cluster together with their heads pointing downward, 3 will always sleep, one will be on guard.

 

[RTR]

The difference in night vision for land animals is full valid, it does not destroy dark-adaptation of our eyes.

Fish are not generally adapted to see red light very well, because of the poor penetration of red in water (first visible wavelength to be absorbed in water). Red light can be used to observe their activitity in the dark (so long as the observer is fully dark-adapted), as they cannot see it as well as we can. The trick there is relative visual acuity in the red bands. We - if dark-adapted - can see them under the red light which they largely ignore, they cannot see us in a fully darkened room.

But a weak red filter on a strong light source will not do the job. You need a dense red filter (photo safelight levels).

For a decent technical expansion of the concept, see:

http://www.photo.net/photo/edscott/vis00010.htm

 

[MikeO]

Jason01, thanks for doing the experiment, I am going to have to do it, I am going to pick up a red light bulb and try it some time.

 

[Matak]

With Luco Brasi.

So. How is it you know Luco Brasi? You've only been here a couple of months.

 

[Harlock]

So. How is it you know Luco Brasi? You've only been here a couple of months.

He sleeps with the fishes and that's all I can say about that lest my Godfather hear me say more...