I have a small 250 gallon pond with a waterfall about six feet high from the bottom of the pond. I keep having problems with the pumps for the waterfall. They are submersible pumps in a well at the bottom of the pond. These pumps last only a few weeks or, at most, six months. The company that built my water feature 20 years ago no longer will honor the warranties on these pumps. What could be going on here? I would appreciate any suggestions for a reliable pump for this small waterfall. Also, I continue to have algae problems. Any suggestions for an effective algaecide also would be appreciated! Bruce,