What I don't know:
- Kind of fish (assuming goldfish or koi)
- Size of your fish. Sounds like a new pond so would assume the fish are small.
- Water temp and climate.
- Water chemistry, ammonia and KH specifically.
- Current pump size.
With that info I could make a guess.
In general... given that size pond and number of fish I would assume the pump could be off forever. For the past several thousand years, up until just a few decades ago, ponds didn't have pumps or water movement or man made bio filters. It has only been the advent of the internet and the sharing of misinformation that people have thought pumps and bio filters are absolutely required in all cases to keep fish alive and water clear.
The myth that pumps and bio filters are always required has a basis in truth as many good myths have. Pumps and bio filters are needed when the fish load (pounds of fish) exceeds the pond's carrying capacity. Many high end koi keepers put a lot of big fish into a small water volume and feed a lot of food all of which leads to requiring pumps and filters. A high end koi keeper with a smaller pond may use more feed in a week than most water garden keepers will use in a year. And the capacity of these pumps and filters all still have to be sized for the fish load. Simply having a pump and a filter isn't enough. Size and type matter. There is a saying in koi keeping that you can grow champion koi in a bathtub given the right pumps and filters.
However, water gardens aren't high end koi ponds. Generally water gardeners let the pond decide the fish load. Fish reproduce and the pond reduces the herd as needed. So therefore water garden keepers generally do very little if any water testing and don't get into any of the sizing issues. Generally they add a pump and something they call a bio filter which does nothing and they're happy. Which is why it's a fun and very different hobby.
If you're checking for leaks be sure to factor evaporation too. Container with basically straight sides nearly filled with water and placed into the pond. Amount of loss in the container estimates evaporation loss in the pond. Many a pond owner has looked for a non-existent leak because evaporation wasn't considered.
