strange fish behavior

[newkidvoodoo]

ok, i wasn't quite sure where to post this, as it has to do with several different things (lighting, fish behavior ect..), so i'll post it here. i recently changed the photoperiod on my tank to begin around noon, and go until midnight. sunday morning, i got up before the lights came on, and noticed that my fish (all of them) were swimming at roughly a 45 degree angle toward the front of the tank. when they would swim the length of the tank, they were tilted towards the front. i sat and watched this for a few minutes, until i came to the conclusion that the light coming in from the livingroom window was tricking the fish into thinking that the front of the tank was actually "up", and they were laying themselves over on their sides in an attempt to swim "upright". when the lights came on at noon, the fish all immediately righted themselves. am i correct in assuming that fish base their orientation solely on light? does the bouyancy of water make this the only sure way for fish to know when they are swimming upright? has millions of years of the sun being overhead confuse the fish when it isn't? am i crazy?

i did search, and found nothing on this. please excuse me if this has been covered before, but in 15 years of keeping fish, i have never seen it.

[DLeDeaux]

This is normal.

Fish actually derive their orientation from their primary source of light. In nature, this is the sun and it isually always comes from above.

In an aquarium, it is usually the lights above the aquarium. But when the lights are off and there is ambient lighting that comes in from the sides, they orient themselves based on this.

I'd be curious to see what would happen if you lit an aquarium only from the bottom. :lol:

[Wasserpest]

Neither you nor your fishies are crazy. Although I have never seen an article about it, I experienced exactly the same "confusion" of fish being exposed to a side window. Weird, huh?

[newkidvoodoo]

what i still can't belive, is that i have never noticed this before! 15 years of having at least one tank in the house, and i just now notice it.

you learn something every day

thanks for the replies...

one more thing... how do fish orient themselves at night when there is no light? i have never noticed any strange behavior before, but you can bet i will be watching tonight...