As a general rule we like to go large as possible when replacing filters for the reasons stated above. I however am from the school of thought that says If it ain't broke... It is hard to argue with success. If that 150 sf filter worked all those years I don't see a real good reason to up-size, particularly since your water condition requires frequent cleaning. Pentair makes a model called "Clean & Clear" that comes in a 150sf and 200sf. The tanks are the same size, just different pleat count on the (single) filter element inside. It also has a twist lock ring that requires no tools and is very, very easy to open and close. Just a heads up if you decide to stay with the same square footage.