I would test the water. The easiest and cheapest way to do that is to buy a pond test kit for about $25 that will test pH, ammonia, phosphates, nitrites and nitrates at minimum.
For about $50 you can test Dissolved Oxygen. Since it doesn't appear to have aeration, I would think this to be critical.
Although there are several other parameters you can and should test for, those will give you the most insight into the viability of the pond.
