The short answer for shrimp lighting
Cherry shrimp are not light-demanding animals. They have no basking instinct and no need for intense brightness; the lamp over a shrimp tank serves the plants and mosses the colony lives in, and your view of their colour. A moderate light on a timer, run for roughly six to eight hours a day, is the working range for most shrimp tanks: long enough to keep mosses and low plants growing and to encourage the thin biofilm and soft algae shrimp graze all day, short enough to avoid the algae surge that overwhelms a small tank. Keep the schedule identical every day, because both the plants and the shrimp's grazing rhythm settle around it.
What light actually does in a shrimp colony
For cherry shrimp, light is a food-growing tool. The surfaces they pick over, leaves, moss fronds, stones, and the glass itself, carry a film of microscopic growth that flourishes under steady, moderate light, and a thriving colony spends most of its waking time harvesting it. Light also shows you the colony's truth: females colour up intensely in a settled, well-lit tank, and saddles and eggs are easy to check when you can see into the planting. Too little light starves the planting, collapses the grazing film, and leaves shrimp clustering on the filter sponge where the film survives. Too much light does not harm shrimp directly so much as it detonates algae growth, swings the tank's chemistry with plant die-off and excess food, and removes the calm, stable conditions this species breeds in.
Shade, moulting, and the small-tank problem
Even in a correctly lit tank, cherry shrimp need places the light does not reach. A shrimp that has just moulted is soft, defenceless, and light-shy, and dense moss clumps, leaf litter, and shaded stone piles are where the colony hides until new shells harden. Babies, too, live their first days deep in moss where the light is filtered. Small tanks under fixed, powerful lamps are the common trap: the whole volume is lit like a stage, with nowhere dim to retreat. Fix it with floating plants over part of the surface, a mossy corner under an overhang, or simply raising the lamp higher above the water. If shrimp spend the bright hours hidden and only emerge at dusk, the tank is telling you the light is too strong for the cover available.
Tuning the hours by watching the tank
Adjust shrimp lighting by evidence, not by the lamp's maximum setting. Green dusting on the glass that shrimp graze down is healthy; thick mats, hair algae strangling the moss, or plants melting under sudden brightness mean the day is too long or the light too close. Change one thing at a time, trimming or adding an hour, and give the tank a week to answer before judging. When adding new plants to a shrimp tank, expect a short algae bloom as they settle and resist doubling the light to push growth, because stability feeds more shrimp than speed does. A colony that grazes in the open at midday, moults safely, and steadily produces babies has its lighting right, whatever the lamp's rating says. Households sharing a shrimp colony can keep its timer setting, plant changes, and headcount notes together with KinsLe's Family Sharing, so care stays consistent from one keeper to the next.