I live in a fairly small town and have heard of many people using this in their spa. You can buy it in bulk here, 20 litres for $50. I'm at the point where I'm not sure, there is no smell which is the main reason I wanted to switch and two cups to get started and a cup a week is what they recommend. You can buy test strips fore $25 for 50 but I'm not sure if I want to buy them too if I'm not sticking with peroxide. I know one person that did this and have found others on google. I'm just not sure at this point but hate the smell of bromine.