Whilst my insomnia keeps we awake I came down stairs to check on the fish and get a drink. I flicked the lights on and found all the fish laying on the bottom of the tank.
Don't panic they seem fine now. However it led
me to thinking do fish know the difference between day and night despite the lack of light of a night time.
If I left the lights on for a week would they assume it's a long day or will they know that the lights are on.
After leaving the lights on for a few minutes they soon started swimming around again.
I don't expect many answers but interesting question I feel.