The short answer for shrimplets leaving the nursery
Young cherry shrimp can move into the main tank with adults when the shrimplets are sturdy grazers rather than near-invisible specks, roughly the size where you can clearly see their red colour, legs, and antennae without pressing close to the glass. In a shrimp-only colony the adults themselves are not the danger, because adult cherry shrimp graze alongside babies constantly in established tanks. The real gates are size against filter intakes, size against any fish mouths in the main tank, and whether the young shrimp can compete for biofilm once they leave a quiet nursery corner.
What has to be true in the main tank first
A main tank ready for young cherry shrimp needs cover that works at shrimplet scale, not just adult scale. Clumps of fine-leaved moss, dense stem plants, and a sponge or fine guard over every intake give a newly moved juvenile somewhere to hide while it learns the layout. Check that the water in both tanks matches closely in temperature and general feel, because a shrimplet moved between very different water often hides, stops grazing, and fades over the following days. Look for leftover food waste or a recent filter clean as warning signs to wait, since a disturbed main tank is a poor first home.
How to make the move itself gentle
Move young cherry shrimp on a day when you are not also doing a large water change, rescape, or filter overhaul in the main tank. Float or drip the nursery water slowly toward the main tank water so the change arrives gradually, then release the juveniles low among moss rather than in open water where fish notice movement first. Feed the adults a small meal shortly before the release so attention sits on food instead of newcomers. For the rest of that day, resist netting, tapping, or rearranging plants to check on them, because constant disturbance keeps young shrimp hidden and off food.
Watching the first days after the move
A young cherry shrimp settling well in the main tank grazes almost constantly, picking at leaves, moss, and the substrate with quick, busy legs, and it moults and returns to feeding without a long disappearance. Brief hiding after a moult is normal, but a juvenile that sits motionless in the open, loses colour, or is found curled and unresponsive needs the water tested and the filter guard checked first. Count roughly rather than chasing an exact number, since shrimplets are built to vanish into planting. If numbers seem to fall day after day, suspect a fish, an intake, or unstable water before assuming the adults are responsible.
A calmer way to time the transfer
Decide the move by readiness signs you can actually see — clear colour, confident grazing, steady growth between moults — instead of by age alone, because a slow-growing nursery batch may need longer than a fast one from the same parents. Note which batch moved, how many went across, and what cover you added, so a later batch benefits from what worked. When several people feed or maintain the tanks, that shared record stops one person moving the next batch early while another is still treating the nursery as home. Recording the transfer date, the batch size, and the post-move checks in KinsLe through Care Teams lets each helper mark a task done with a timestamp instead of relying on memory.