I wanted the top water to keep moving to aerate the water and so far with the new pond i had algae for 1 week and then set this up but with a ball valve at first like i had with my other pond .I don't have a skimmer but have 2 filters .Don't really need a skimmer since no leaves really fall in the pond .I bought an aerator any ways ,don't know why .I think it really helps the water quality ,just like growing plants in my filters .put 2 of them in my waterfall also .Last pic was taken of waterfall after having them running all summer long .I do sort of quirky things to just see what happens .You can also see that in some of the stuff I create and build .I don't like normal predictable