Your old tank acted as a settling tank, and provided a place for solids to settle. Now you are filtering all of them out. If it were me, and I still had the old filter and housing, I’d install the new filter in parallel with the old one, with valves before and after each filter. This way I could have one filter on line at a time, and if I needed to switch filters, I could just open and close valves to put a new filter on line. Then I could change the old filter at my leisure.