this had been discuss a lot of times....the conclusion....do it at your own risks.....
so much so that it might contain 100% of minerals direct from the sea, it might also contain harmful bacteria tat u won't want to introduce into your precious tank.....deepblue makes sense, y endanger $1000 worth of LS with something tat u are unsure of.....the safest bet is to steal the sea water from AT's, deepblue, and other sps freaks' tanks...confirm 100% squeaky clean.....
u might wanna do a little experiment yourself 1st....another way is to quarantine the sea water that u purchase for at least 2-3 weeks b4 adding to your tank....i've thought about this b4, but it is too much of a hassle....i will end up using it directly...