One other option, and it ain't cheap, is reverse osmosis (RO) filtration. I know there's at least one company in southern CA doing it so there might be one up in your neck of the woods.

RO will remove almost everything from your water - calcium, salt (measured by TDS), CYA, Carbonates, borates, metals, etc. I'm not sure if companies will RO with algae present or not. You typically have to let your FC drop to zero (FC destroys the RO membrane material) and they filter and rebalance the water for you. The recovery fraction for an efficient, industrial RO system is approximately 80% so you would still need to add some fill water.

Last time I looked into it here in southern AZ, it was about 2X the cost of water replacement.