Sounds like your metal free!

You do understand that borates make your pool more resistant to algae, but don't guarantee and algae free pool?

Assuming that you do, for a 30k gallon pool, you'll need about 23 boxes of borax (~$4 each) and 8 gallons of 31% muriatic acid (~$8 each), so the total cost would be $160. It is a permanent addition, except for leaks, backwashing and splashout.