Hello, First time in forum. I have a Softtub Spa 200, and stopped using chlorination 3 years ago, instead started using hydrogen peroxide. There have been no problem since with algae or bacteria. The spa is 200 gal. and I use one 32oz 3% bottle twice a week. Dollar Store has it for $.88 a bottle. For larger hydrogen peroxide 35% is available on line cheaply in large quantities.