Yes, cherry shrimp need a heater. Cherry shrimp need a relatively warm water temperature between 65°-80°F (18.3°-26.6°C).
Even if the cherry shrimp tank is located in a warm room, the temperature can still fluctuate throughout the day. For that reason, a heater needs to be installed in the tank.
Cherry shrimp are extremely hardy, so suboptimal water temperature won’t kill them immediately. With that said, a suboptimal temperature can still lower the cherry shrimps’ immunity, cause various diseases in the tank, create molting complications, shorten their lifespans, and prevent conditions for breeding.