I was having a problem with IO salt forming a rim on the blue RubberMaid tub I mixed it in. This was after 24 hours with a powerhead and a heater trying to form a SG
of 1.022-1.023. No matter what I did, it kept coming back, like some of the salt didn't want to dissolve.
I hadn't noticed it before probably because I was using a white container before, but it showed up nicely on the blue tub.
So I bought a plastic bottle of Ocenaic salt and it mixed up great. No salt rim and great Ca
+ numbers. It was totally mixed after about an hour in 10gal, but of course, I let it sit overnight perculating just in case.