Okay, I've got my answer. Diamond Crystal states that its Sun Gems with red out is designed for iron removal up to 2 ppm cLear waterm iron.
For water supplies with iron above this, you should also use a resin cleaner in addition to the red out pellets. They suggest Iron Out brand, but I would imagine any product that has a similar composition would be satisfactory.
I also read that a periodic (quarterly or less if needed), is also advisable to remove all traces of any iron that may still be attached to the beads (sticky iron that the weaker red out can't oxidize properly).
So I have my answer. Use good, clean pellets with red out; and in addition, a resin cleaner quarterly or semi-annually. (I will use Sears cleaner as I trust this brand).
My softener manual also recommends sanitization when first put in service (I didn't do this) and may be needed with some water types periodically (annually or bi-annually I would guess).
To do this, you pour 2 tablespoons od Clorox down the down the brinewell and immediately run a cycle. (Can be done with or without salt). So I'll add this to my regular softener service.
Thanks to all who replied.