I replace an iron filter, that failed due to low backwash rate, with a Birm filter with AIO3. Does it make sense to repurpose the old 1.5 cuft 7000sxt filter as a carbon prefilter? I was thinking a Zeolite bed with GAC and KDF cubes. MY thinking for carbon at all was to protect the Birm after well sanitizing which I do once or twice a year. My raw water tests to only 0.5 ppm ferrous iron with a PH of 6.8 with a light sulfur odor and IRB as noted by slime in the toilet tanks. I know I should have had a water test done but I haven't.