I have to be careful with this one as I did work for this manufacturer for 6 years. My advice with the Laguna Pressure Flo is to make sure that you over size the filter unit. For example, if your pond is 1500 gallons, go with the PF-3200 (#PT-1506) as there is no such thing as too much filtration. With the flow rate if the water moves too fast through the filter, there will not be enough contact time for the biological filter to break down the organic waste. Also, if the water goes through too fast, their will not be enough time for the UV to act properly in destroying the waterborne algae. My current favorite is the Tetra Pressurized filters, but don't follow the manufacturer's flow rates as they are too fast. I suggest going with the Tetra Bio version and then running an Emperor Aquatics UV after the filter. I suggest Emperor as their products are used mainly by zoos and aquariums. I also noticed that some one had mentioned making your own filter by going with a Skippy. I love gravity fed filters and what i suggest doing to the Skippy is to add an aerator in the mix as this will boost the performance of the filter greatly. If you have the space and don't mine the appearence, the Skippy is a good way to go as well. If you have additional questions, you are more then welcome to give me a call at 800*722*8877...Chris