How many gallons how often? Depending on your set up you could keep a 55drum or 2 full and siphon them into your rays. If water sits couple weeks+/- you'd be safe using for water change chemical free. And if you are not using heaters (don't know where you live) the replacement water would be the exact temperature
The product you linked to doesn't remove 100% of either chlorine or chloramine, you may want to search for a dedicated stand alone system that uses cartridges specifically for chloramine AND would still need to test the processed water using chlorine test strips and ammonia test strips to verify it is good.
There were quite a few topics on MFK for a system members used.