As previously this is website is to focus on fishes and their welfare rather then the plants. I am not a botanist and wont claim to be so I will later recommend resources there. The focus being fishes means keeping their welfare and biology the benefit.

Fishes likely do benefit off a day night cycle, circadian rhythm if nocturnal, at depth or not. There is no harm in providing lighting and providing this. An important element to consider is if fishes prefer dimmer lighting and catering for it there, providing areas of dim and bright lighting even better as gives them choice.

Lighting and algae is certainly a big topic and generally it seems to be largely nutrient influenced. I’d be more tempted for the fishes welfare to change lighting hours seasonally.

There is an exception to all the above, in goldfishes and some others it is beneficial to increase the hours and have certain lighting e.g. UVB reptile lighting. Why might it be beneficial? That lighting contributes to maintaining any black and contributing to other colouration. Outside time for those fishes definitely does and the seasonal variation might do as well, another discussion for another day.

UVB

Not really for the beginners page but something I want to research further for fishes in general. Does it have benefits? Maybe……