Here's what i do.
I (at any given time) have 2-3 gallons of tap water sitting with the cap off. Every day I well put the call on, give them a heavy shake and take the cap off and let them sit again.
Before I use the gallon I will put the water in the bucket that I mix my nutes and throw an air stone in and let that bubble for a hour or whatever (I can lose track of time).
Then mix my nutes, pour it all back in my jug, feed my plants and call it a day.
I know it may sound like a lot of work or waste of time but I use to use that dechlorination stuff and found it was a waste of money.