I've noticed that all of my fish (angels, barbs, tetra, gourami) seem to orient themselves parallel to the brightest light in their environment. During the day they are vertical, but at night when I have a lamp turned on that is off to the side of the tank, they are all tilted toward the light, almost horizontal. They have always done this and are eating and there are always fry swimming around, so I know they are all healthy. I am just curious if they do in fact orient themselves toward the light or if its just coincidence. Even though I know they do that, its always slightly concerning when I go over and see my fish swimming sideways.
How do fish know which way is up?
- Thread starter matseski
- Start date
I have only seen silver dollars do that... its because of the circadian eye.. but fish also have air bladders and probably other ways of keeping orientation. Fish have different requirements for this, just like birds. Birds that don't migrate for example tend to have less orientational instincts than ones that do.
If you mean how do fish know how to balance themselves, likely the otolith for most species, although fish being so ancient and diverse, I would assume many species have other methods as well. This is an inner ear structure which land animals likely inherited from fish.
If you mean how do fish know where the surface is, then some likely use light as an indicator and thus orient towards that. The swim or gas bladder might help with that in dark environments, and of course some fish species can see light outside the range for which humans see so "visible" light isn't the only light that some fish might use.
Although not the same per se, a human can lay down on his side in a pitch black room and know that he is sideways and which way is "up". I assume that lizards, snakes, alligators, aren't confused either in a similar environment.
If you mean how do fish know where the surface is, then some likely use light as an indicator and thus orient towards that. The swim or gas bladder might help with that in dark environments, and of course some fish species can see light outside the range for which humans see so "visible" light isn't the only light that some fish might use.
Although not the same per se, a human can lay down on his side in a pitch black room and know that he is sideways and which way is "up". I assume that lizards, snakes, alligators, aren't confused either in a similar environment.
