chlorox is small amounts will be fine. Its no different then pool water or tap water if you have city water. Too much could cause a burn problem.

Why are you going to treat the water?? skeeters, algea, bacteria.

If it is a closed system,(skeeters cannot enter) then I would not treat it at all. Get dunks for them instead.
For algea you can use barley in old pantyhose or onion bags.

Thanks for the response billinpa!

It's not a completely closed system...there's about a 1/2" gap where my pipe enters the tank, so skeeters could be an issue. I suppose I could try to seal it off, but I would still have algae to deal with as it is going to get a fair amount of sunlight.

Why you will treat rainwater with clorox ????? why not with
fluoride and all this junk they ad to the city water distribution.rain water is the water from haevens and believe me the nature know best .If harvested in good condition is the best water to drink.and better for our health filtered and pasteurised.Plants grow better,have more fruits with rainwater it looks like they are smarter than we are

louis

I would recommend you will treat the water by electrolysis, if you have an device. Electrolysis...?? I know most of people feel strange or even skeptical.

If you electrolyze water "properly", you will get oxydised and alkalized water. Oxydised water is a superb organic sterilizer with no remnant that will kill disease bacretia and viruses in less than 30 sec., and then apply alkalized water.

Alkalized water does not only neutrilize the oxidized water, but also makes plants healthier and stronger by enhancing activities of roots and lieaves.

It will be hard to believe for you, because there is no such thing in the USA yet. This concept has been used in Japan for more than two decades, and greatly improving produce quality and increasing crop by 15% - 30%.