I spent 3 years always letting my res water sit out and airate to get the chlorine out. A little over a year ago I started looking for an alternative to H202 to steralize my res. After alot of reading I found people were using chlorinated water with great success on their clones instead of bottled or RO or anything else. So I tried it, and low and behold I started getting roots 1-2 days faster. A few months later after more reading and talking to a couple people I started using a chlorine solution in my res instead of the H2O2, and its been working great. As you read into it, you'll find that Chlorine actually has benefits and is very natural in a growing plant at reasonable levels. I mix about 1/2 tsp of pool shock chlorine into 1 gallon of water to make a solution. I then mix that solution with my res water at 1 oz per gallon every 4 days or so. Its been working great for about the last year. If you look there are actual products being sold one is called clear rez, and they are basically a chlorine solution that is premixed. The pool shock cost me 9 dollars last year and you can't even tell I have used any out of it yet.