The short answer for angelfish lighting
Angelfish do not need bright light; they need moderate light, delivered on a predictable schedule, with shade they can choose. A timer holding a steady day of roughly eight to ten hours suits most angelfish tanks, and the exact brightness should be set by the plants in the tank rather than by the fish. In a fish-only or lightly planted aquarium, a modest light run at partial strength is plenty. In a densely planted tank, the plants may demand more intensity, and the angelfish's share of the bargain is cover: tall vegetation and floating leaves that break the light into lit lanes and shadowed retreats across the height of the tank.
Why glare bothers a tall, slow fish
Wild angelfish live in slow, vegetation-lined water where light filters down through surface cover and between tall plants, and their deep, narrow bodies are built to slip sideways into that shade. Under bare, intense aquarium light they cannot escape the brightness, and the results are familiar: fish hanging motionless in the one dim corner, colours and dark bars paling, pairs growing touchy, and shy individuals refusing to cross the open centre to feed. Angelfish also startle at sudden changes, so a light that snaps from darkness to full power can send the whole tank bolting. Predictability matters as much as intensity. A fish that knows when light comes, how bright it gets, and where the shade is will use the whole tank calmly.
Setting the schedule and brightness
Put the light on a timer from day one and keep the same on and off times, because an irregular schedule unsettles fish more than a slightly long day does. If your light is dimmable, begin at a moderate setting and adjust in small steps over a week, watching the angelfish rather than the spec sheet: relaxed cruising at all heights means the level is right, while fish crowding the shadows means it is not. A gradual ramp up in the morning and down at night, if the light offers it, removes the startle of sudden switching. Where room light reaches the tank before the timer starts, that soft pre-light is a bonus the fish genuinely use. Avoid leaving lights on late into the evening to extend viewing; a long, bright day feeds algae and steals the dark rest period the fish need.
Plants, shade, and pairing the light to the tank
Tall plants are lighting equipment in an angelfish tank. Stems and broad leaves reaching toward the surface slice the light into columns and shadows, and a partial raft of floating plants dims the top layer where angelfish often cruise and where breeding pairs claim territory. Arrange at least one genuinely shaded zone, ideally at an end of the tank, while keeping some lit open water for feeding and display. If algae begins coating leaves while the fish still hug the shade, the day is too long or the light too strong for the planting to use, so shorten the schedule before blaming the fish. Households sharing an angelfish tank can keep its timer settings, brightness level, and shade-planting notes together through KinsLe's Family Sharing, so nobody resets the light on a whim.