I've been using aquavitro salinity, and I like it so far. The bucket is really dang heavy though... sort of wish they'd made it in the "normal" 5 gallon size, although having a new bucket size/shape is a side benefit
agreed. It's the same latching system that is used in small scale industrial chemicals that absorb water from the air-- much better at keeping moisture out than the pop-top kinds.
Natural Sea Water has a natural value of 0.030 mg/L of Copper from what I've read. That was shocking to me as well. In our reef systems an acceptable range is 0.000 to 0.030 mg/L