dont use permanent hypo on your DT. thats not a cure, thats just a suppressive method. if there were diseases in the water, they would just lay there dormant until, eventually, the salinity crept up enough to allow it to take off. also you dont really need to qt inverts because the majority of the most common diseases do not affect inverts, nor do they usually carry them. as previously stated, a QT tank doesnt not need to have any form of medication at the beginning to be effective. If, at any point along the QT timeframe, you recognize and diagnose an illness, then treat accordingly. Yes you can proactively treat, but 1)youd have to treat broad spectrum, or even blindly. which the broader the treatment, usually the less effective it is against specific illnesses. and 2) you are subjecting the fish to a potentially uncomfortable treatment that very possibly dont need to.