I use tetra aqua safe I believe. When I do water changes, the day before, I fill a 5g bucket to the line. And add 2.5ml using a syringe. Put my air stone in and bubble the gas out all night. Next morning if I need to do a WC
, I just take out however much is needed and I use the water in the bucket, and fill it back up and repeat the process.
I end up using all the water in the bucket so I make a new batch of water everytime.