i had a pond 15X4 feet 3feet deep about 800gallon,bought a new little giant pump 4900g/h which was the pump i had 2006,the 3 tier waterfalls works good for 3hours later it start trickling due to less water at the skimmer,after a minute it start flowing good again then a minute later it start trickling down,shut off the pump ,afraid it will burn out ,several days past the water level never goes down,i dont know the problem