When visiting an aquarium, it's often not allowed to take photographs with a flash light on. It is said that the flash light with very high intensity is harmful to the displayed life forms.

I respect that and try to capture images without flash.

I'd still like to know how flash light interacts with the animals (or even the plants) in an undesirable way? Is it harmful because they are not used to it?

The light emitted from the arc of a welder for example is so intense, that it destroys the human eye. Laser is another example. Technology is so advanced that we can produce harmful light sources that not even the winking reflex can protect us against. Maybe a flash light used for photography is the welding arc for aquatic life?

Additional light can increase growth of algae, which would in turn influence the (very little) ecosystem in an aquarium. On the other hand, I don't think the short bursts of light from photographic flashes introduce enough light to have an impact. Or do they?

The motivation for this question is not to be knowledgeable about what creatures are not harmed by flash in order to fry them in light. Advancements in camera technology make it unnecessary to add more light to the scene in the form of flash light. What made me curious about it is that except for the industrial light sources mentioned above, we rarely consider single bursts of light to be dangerous for us dogs humans. We are much more concerned about the continuous sun light.

meta: I'm not knowledgeable enough to tag my question properly. Entering "fish" gave me ichtosomething. But this question is not only about ichtosomethings, but aquatic life in general. Possibly including plants, too. Sorry if this is not appropriate. An edit that chooses more appropriate tags and removes this paragraph is well appreciated. Thanks.

When visiting an aquarium, it's often not allowed to take photographs with a flashlight on. It is said that the flash light with very high intensity is harmful to the displayed life forms.

I respect that and try to capture images without flash.

I'd still like to know how flash light interacts with the animals (or even the plants) in an undesirable way? Is it harmful because they are not used to it?

The light emitted from the arc of a welder for example is so intense, that it destroys the human eye. Laser is another example. Technology is so advanced that we can produce harmful light sources that not even the winking reflex can protect us against. Maybe a flashlight used for photography is the welding arc for aquatic life?

Additional light can increase growth of algae, which would in turn influence the (very little) ecosystem in an aquarium. On the other hand, I don't think the short bursts of light from photographic flashes introduce enough light to have an impact. Or do they?

The motivation for this question is not to be knowledgeable about what creatures are not harmed by flash in order to fry them in light. Advancements in camera technology make it unnecessary to add more light to the scene in the form of flash light. What made me curious about it is that except for the industrial light sources mentioned above, we rarely consider single bursts of light to be dangerous for us humans. We are much more concerned about the continuous sunlight.