Chlorine is the common treatment and preventaive used by the commercial green huouse trade. I have been using it for iver 10 years. Flairform Pythoff is the most widely sold. They sell to different d formulas. One is jsut RO water with chlorine bleach added. The other is RO water with chloramine added. The chloroamine does not outgass as quickly as regular chlorine so it does not have to be added as often.
Here is a link to therir site that gives links to its MSDS on their products.
http://www.flairform.com/Products/pythoff.htm Look at the 25 g/L link. Regular chlorox bleach is about 7.5% sodium hypochlorite. You need only add enough chlorox to RO water to obtain the % of chlorine provided in Pythoff. Flairforms commercial strength is 2.5% or chlorox diluted to 1/3 strength. Here is the label of their bottle.
http://www.flairform.com/downloads/py_commercial_label.gif
As can be seen very little is added to the water. It works out to adding 1 ml or 2 ml of the diluted bleach to every 6.6 gallons of water. You can dilute the bleach to waht ever concentration you want that makes its use the easiest. AT 1/3 third strength one teaspoon of chlorox bleach is good for 16.5 to 33 gallons of nutrient water. Typically one starts with 1 teaspoon (diluted) per 16.5 gallons then every two days add 1 teaspoon (diluted) for every 33 gallons to replaced used through oxidation reactions and by outgassed chlorine.