water storage

Just got 4 food grade barrels for water storage.I have cleaned them with a vinegar and backing soda solution, and plan to do a final rinse with a mild mix of bleach and water. What do you recommend as storage solution.I have seen the mixture they sell for $15. but would like to find a cheaper way. So far bleach is the cheapest way I have found.I plan to get a water filter soon,and will use it when we need to use the water.Thanks