Tannis Problem

I live in rural Ontario, Canada. I have a tannis problem, really noticeable in the bathtub. Our water is drawn from a river that moves pretty constant.
What can I get to remove this tannis from my water.
I have read about Kinetico Resin based Tannis Filters, but have had no luck finding one for sale here.
I have also been reading about softeners and am wondering about them as well.

Thanks,
Stephen

I have a double filter system by Rainfresh.

The first filter is 1 micron extras fine pore filter cartridge.

The second filter is 5 micron chlorine taste and odour cartridge.