The short answer for a nocturnal grazer
A bristlenose pleco's lighting needs are almost the opposite of most aquarium fish: it asks for dim days and a proper night. This is a dusk-and-darkness feeder that spends bright hours tucked under wood or inside a cave, then emerges to rasp algae and biofilm from surfaces once the lights go down. Run the tank lights for the plants and for your viewing, on a timer of around eight hours, and treat shade as a core furnishing rather than decoration. If the pleco can always reach a genuinely dark refuge, moderate community-tank lighting overhead is fine; if the tank is bare and bright, even modest light becomes a problem the fish must endure all day.
How a pleco experiences your light schedule
Bristlenoses read light as a clock. Bright, long days push them deeper into cover and shift all their feeding into the night hours, while a stable, shorter day with a clear dusk lets them begin grazing as the light fades, which is when keepers actually get to watch them work. Sudden full-brightness switching can send a pleco bolting for cover, sometimes clumsily enough to scatter substrate or dislodge decor, so a light that ramps down in the evening suits them. A dim blue evening setting, used briefly for viewing, disturbs them far less than white light at full power. True darkness overnight matters too: a tank lit around the clock by room lights or a glowing standby setting never gives this fish its working hours, and keepers then wonder why it seems to do nothing.
Building shade into the aquascape
Furnish the floor like a pleco's map of shadows. At least one cave it can fully enter and turn in, a piece of driftwood with an underside it can cling to, and planted or rock overhangs that shade stretches of substrate give it a choice of refuges across the tank rather than a single contested hiding spot. Place some grazing surfaces, glass, wood, and smooth stone, where they receive partial rather than direct light: a light dusting of algae on those faces is the pleco's pantry, while surfaces under fierce light either bake bare or grow algae faster than one fish can crop. If there are two plecos or other bottom fish, multiply the caves; a single prized cave under bright light becomes a battleground at dusk.
Balancing plants, algae, and the pleco
The lighting tension in a pleco tank is triangular: plants want light, algae answers light, and the pleco wants neither extreme. Enough hours for healthy plants, delivered steadily, grows a gentle film the fish can harvest; too many hours grows hair and mat algae a bristlenose largely ignores while smothering the plants. If the pleco's belly looks sunken or it rasps the glass frantically at lights-out, it may simply be underfed once the tank's natural film is cropped, and lighting changes are no substitute for offering vegetables and sinking foods after dusk. Judge the schedule by the whole picture: plants growing, film present but not rampant, pleco out and grazing at night. Families running this tank together can use KinsLe's Family Sharing to keep the light timer, cave map, and after-dark feeding notes where every helper sees the same plan.