Most of the precipitated iron either sticks to the sides of the tank or stays in suspension and goes to the iron filter where the media removes it. Anytime I manually flush the contact tank, it runs clear within seconds.
My Banjo filter traps about a teaspoon of sand in a month so flushing it once a quarter works for me.
I have my iron filter programmed to backwash 3 times a week. Once a quarter, I also do a few back-to-back manual backwashes at higher pressure. I open up the micronizer bypass for more GPM and jack the pressure to 80 PSI.