Whether or not you use an entrance reducer is a matter of choice, and can be determined by local conditions, such as temperature and what types of animals in your area might get into the hive. For example, bee-eating lizards might be an issue in one area, and not be present in another. So advice from local beekeepers can be really helpful.
Entrance reducers can also be helpful for weak hives in danger of robbing or for cold climates.
You might have heard the old adage “put one question to two beekeepers and you’ll get three answers” – so we always recommend chatting with your local bee club or putting your question to the Flow Forum as well, so you can get a wide range of opinions and see what resonates.