Light is this fish's food supply
Most lighting questions are about how fish look; this one is about what a fish eats. A Siamese algae eater spends its day working — mouth rasping along leaves, wood, stone, and glass, harvesting the soft algae film and the tiny life growing within it. That film only exists where light reaches, at a rate set by how bright the light is and how long it runs. Lighting a tank that houses these fish is therefore partly a feeding decision, and both extremes fail them: a dim, short day grows almost nothing to graze, while a blazing long day grows the wrong things.
The working target for most planted community tanks with Siamese algae eaters is moderate-to-bright full-spectrum light for eight to ten hours daily, timed, with the fish also receiving proper meals of their own. Grazing supplements a diet; it never replaces one.
What they eat, and what they leave
These fish earn their name on soft green algae and the early, tender growth on leaves and hardscape, and young fish also pick at some hair-like algae while it is short. What they largely leave alone is the tough, dark, brushy growth that establishes under excessive light and neglected conditions. That distinction defines the lighting ceiling: once the day runs long enough that hard, wiry algae outcompetes the soft film, you have more algae than before and a fish swimming past most of it.
So when algae worsens in a tank that already has algae eaters, the fix is almost never more fish. Shorten the day in half-hour steps toward eight hours, check the timer is actually obeying its setting, and let the eaters hold the line on the soft growth while the tougher growth starves back and can be trimmed away on leaves it has ruined.
Plants are their furniture
Between grazing bouts, Siamese algae eaters rest in a characteristic pose, propped on their fins atop a broad leaf, a piece of wood, or a flat stone. A planted layout gives them those perches and grazing surfaces in one: broad-leaved plants under decent light stay firm enough to hold a resting fish, while weak light makes the same plants thin and floppy. Light strong enough for the mid-ground planting is therefore part of this species' welfare, not just the aquascape's appearance.
They are also strong, streamlined swimmers that use the tank's full length, and open swimming water in front of the planting should stay unobstructed. Even light across the tank avoids a bright end the fish overgraze and a dim end where uneaten film thickens on the glass.
Rhythm, schooling, and observation
Kept singly these fish can grow pushy with age; in a small group they are busier and more settled, and a well-lit tank during the day is when you see that social grazing behaviour at its best. Their lit hours should overlap yours — mid-morning to evening on a timer suits most households — because a healthy eater's constant working is also your early-warning system. One that stops grazing, hides, and loses its clean black stripe's contrast is a fish to check water quality for, promptly.
A true dark period matters as much as the day. These are diurnal workers; a tank that never goes dark leaves them restless and blurs the algae growth cycle the whole arrangement depends on.
The weekly balance check
Once a week, read the tank like a gauge: a light dusting of soft algae returning between cleanings, plants firm, eaters working steadily — the light is right. Bare surfaces and thinning plants — add a little time. Wiry tufts spreading on wood and leaf edges — take time away and review feeding, because excess food plus excess light is the usual partnership behind it.
Small tanks drift out of balance quietly when checks are skipped, so KinsLe Care Teams lets you hand the weekly algae review and the eaters' supplemental feeding to a named helper, with completed tasks marked by a timestamp.