BloomnBill,

I use a regular 1:1:1. I heard people add extra dolomite.
I am afraid that however well the coir is rinsed - it will still have some salt plus when it starts falling apart, it actually inhibits the growth. Our Korina used coir - and then she started having problems - so she investigated the subject thoroughly - I think coir is something to use for the basket lining of annuals, not for inside plants.

I didn't try any sphagnum on it, should be OK except that it can add to the acidity of the mix. So may be dolomite can be of advantage in this case too.

I.