my bigger tank is on a timer so it gest 10 hours regulated.
my corner betta/ADF tank, which is planted - is on a human time and i work shifts that can start at 7am or finish at 11pm so i just give it 12 hours - switch it off the opposite time i got up at. im usually around at that time, but its not unusual for me to not get home its received up to 20 hours in the past. i dont make a habit of that though, maybe 14-16 hours.
but considering i get rougly 18 hours sunlight a day right now and the nights are still getting shorter, the fish should be thankful for all the "sleep" i give them lol