I changed out 10g of water twice a day (in a 75g tank) for 2 weeks when I cured my live rock.
My theory being that the rock has the necessary bacteria already on it, my job was to keep as many of the critters alive as possible. The nitrates started to drop after 2 weeks so it didn't prolong the cycle and at the end of it I had numerous snails, chitons and urchins.

Oh and i just used tap water until the cycle finished and then did a 100% water change with ro water