Drain the remaining water from the pond (Image 1). Pressure wash the concrete surface of pond's interior, then apply a pond caulk (Image 2) to all major cracks. Because caulk is flexible and will shift with the crack, smooth caulk with a trowel for better and wider coverage.
Another vinyl hose is attached to the opposite side of the filter with plastic black clamps, for the clean water to be returned back into the pond. Create a waterfall-like effect by hiding the vinyl hose under a pile of rocks, but only enough to hide, as the hose can be crushed by too much weight