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re incident light and fish listing

Date: Thu, 18 Feb 1999 14:54:41 -0800
From: "alex pastor" <alexp at idirect_com>
Subject: angle of incident light and fish

This might seem really weird, but let me explain.  When I was a kid I 
had a 10 gallon aquarium sitting on a dresser in a south facing bedroom.  
For some hours during the day the tank got direct sunlight.  I noticed 
that the fish did not assume a straight (side to side, not nose to tail) 
position.  They were always at an angle when I could see them straight 
from the front.

When we moved and my bedroom window faced north, all the fish assumed a 
straight orientation.  There was of course, never any sun shining in on 
them at any angle whatsoever.

Well, people are writing about mirrors and such, so I remembered this

I know it seems strange, and yes I had and have my head straight on my 
neck. Could the predominant incident angle of strong light have any 
influence on the way in which fish ?balance themselves in the water?  I 
swear, what I saw was real and true.  And no, I have not lost all of my 
marbles, just some of them.

g. kadar>>>>

Yes, I agree with you.  Fish use light to determine which way is "up". 
It seems that light is not the only factor, however, because they don't 
start to tumble around when the lights are off<g>.  I find it quite 
entertaining to shine a flashlight on my yellow tang when the tank 
lights are off....he almost instantly rolls over onto his side to make 
the light source "up".

matt, who got frustrated with canister filters in general and threw them 
out in favor of sump systems many years ago.

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