Originally Posted by maxalmon
One of my tanks has an auto topoff with a reservoir that holds about 2g of water, can both the A and B part to the this reservoir?
no - there's a reason why they are in their own container. Like reefreak29 said, they'll cancel each other out. Then, all you'll be added is salted water.
** I actually tested this once. I added both parts in a cup. All I saw was a milky substance which is probally CaCO3 solids. I tasted the water and it was salty. I am still living.