Proper pool maintenance is important, no matter what size of pool you have. Otherwise, green algae can develop, the water can become cloudy, and the pool won't be as safe or as enjoyable to use.
The good news is, a plunge pool will require fewer chemicals than a full-sized pool to stay sparkling, but you will still need to test and sanitize it regularly, including adding pool shock. Fishing out debris using a pool net and using a pool vacuum is also essential.