We have an established 500-700 gallon water garden. Plants and fish are there, as well as aeration. There is plumbing for a pump to move water from garden to waterfall about 4 feet up. I am looking for a pump to move the water. The one in there is much too powerful and falls over when in operation due to pressure. Is there a non-submersible pump that will meet our needs that will handle "dirty" water, as the one in there also "gunks" up frequently? My husband has even considered a pool pump/filter system. We have had an issue with algae, as it is in partial to full sun. Currently, plants are growing to cover most of the surface, so this will hopefully aid in this issue. We have used algaecide, only to kill fish several times.