Cherry shrimp break the usual stocking logic, because the number you buy is not the number you keep. A starter group settles, females carry eggs, tiny shrimplets appear in the plants, and the colony finds its own level over the following months. The honest answer to how many a small tank holds is therefore about conditions rather than arithmetic: give a modest starter group the right surfaces and stability, and let breeding, food supply, and survival rates settle the population for you.
The Starter Numbers
For a small tank of 10 to 20 liters, begin with a starter group of ten cherry shrimp. Ten is enough for a mix of males and females, enough for breeding to start once they settle, and few enough that a young tank's water and food supply are not strained while it matures. A settled colony will grow into dozens in that same 10 to 20 liter volume, which surprises new keepers who expected to calculate a final headcount in advance. Resist adding a second batch quickly to speed things up, because a sudden jump in animals tests water stability before the plants, surfaces, and filter growth that support them have developed. Let the first group's survival and first shrimplets tell you the tank is ready for growth.
Food Surface and Stability Set the Limit
No per-liter or per-shrimp formula governs this colony, and any tidy rule of that kind misleads. What limits numbers is food surface: shrimp graze biofilm and algae from plant leaves, wood, substrate, and glass all day, so leafy, textured, well-grown planting supports a much larger grazing population than bare glass and fresh substrate in a tank of the same size. Water stability is the second limit, because small volumes swing quickly, and a colony that thrives under steady temperature and clean, consistent parameters can crash after one large careless water change or an overfed weekend that fouls the water. Feed sparingly, in small amounts the colony clears within a couple of hours, and treat uneaten food as a sign to reduce the next portion rather than as generosity. As grazing surfaces thin and shrimplets compete harder, growth naturally slows, which is the colony signaling its ceiling without any formula.
Living With a Growing Colony
Tank mates change the colony's ceiling as surely as surfaces do. Fish that hunt shrimplets can hold a breeding colony at a fraction of its natural growth, while a shrimp-only tank lets nearly every shrimplet that finds cover survive into the grazing population. Plan the starter group of ten with the tank's other residents in mind, provide dense plant cover and fine-leaved refuges before the first females release young, and remember that a colony growing to dozens needs those refuges at every size, not only during its first fragile weeks in the tank.
Count roughly, not obsessively: a weekly note of how many shrimp you can see, how many females carry eggs, and whether shrimplets are appearing tells you more than a daily census you can never make accurate among the plants. Keep filter intakes covered with fine mesh or a sponge guard, because shrimplets are small enough to be drawn in, and keep copper-based treatments out of the tank entirely, since copper harms shrimp even at levels sold for other purposes. When numbers genuinely outgrow the grazing, move surplus shrimp to another keeper or a second tank instead of letting competition thin them through hunger. Stable water, steady food surfaces, and patience do more for this colony than any purchase. A partner reviewing the Family Sharing notes on KinsLe learns tonight's pinch of food, yesterday's count, and whether grazing surfaces look thin.