The short answer for a cherry shrimp colony
In most homes, no. Cherry shrimp — the red form of a hardy dwarf shrimp farmed and kept all over the world — tolerate a wider temperature span than almost any fish in this hobby, and they breed happily in unheated tanks at ordinary room temperature. Where a tropical fish would fade in cool water, a cherry shrimp colony simply carries on grazing. The honest answer is that this is one species where the heater is the exception, not the rule, and adding one thoughtlessly can create the very danger you were trying to avoid.
What temperatures cherry shrimp actually like
Cherry shrimp stay active and breed well roughly between the high 60s and the upper 70s Fahrenheit. Toward the warm end their metabolism speeds up: they graze more, molt more often, and females carry eggs more frequently, though they also live a little faster overall. Toward the cool end everything slows — less breeding, longer gaps between molts — but the shrimp are not suffering, just idling. What genuinely harms them is instability. A tank that swings several degrees between a sunny afternoon and a cold night stresses shrimp far more than one that sits steady a few degrees cooler than ideal.
When a heater does earn its place
Consider a small heater if your tank room regularly falls into the low 60s in winter, if the tank sits against an outside wall or near a drafty window, or if your household temperature swings hard between day and night. If you do add one, choose a small unit suited to the tank's size, guard it so shrimp cannot rest against the hot surface, and pair it with a thermometer you actually read. In a small shrimp tank the margin for error is thin: a malfunctioning heater can raise a few gallons of water to lethal levels in hours, which is why many experienced shrimp keepers prefer a cool, steady room to a heated, risky one.
Running the unheated shrimp tank well
Keep the tank away from radiators, sunny windows, and exterior doors so the room's natural stability works for you. Top off evaporation with water of a similar temperature rather than a cold splash straight from the tap, and match temperature as closely as you can during water changes — shrimp feel a sudden cold change instantly and may molt in response to the shock. Watch the colony rather than the dial: shrimp spread across the plants grazing calmly are comfortable; shrimp clustered motionless for days in cool water are simply slowed down, while sudden deaths after a temperature swing point to instability as the culprit. A shrimp tank is a shared household pleasure more often than not, and KinsLe's Care Teams lets you assign the weekly water change, the feeding days, and the filter checks to whoever is home, with each finished task marked off so nothing gets doubled or missed.