Agree... just change the water. I wouldn't even bat an eye over 16g.
The thing is, which your LFS is kinda forgetting to tell you, is that when you're done cycling you more than likely will have a large amount of nitrates. The easiest way to get rid of those and start again with pristine water after the cycle is to do either one big 90-100% water change, or a couple 50% water changes. At that point, you have no critters in the tank and the good bacteria don't live in the water, so swapping all the old yucky water for good water is easy.
However, assuming that you've spent $$ in pumping additives in your tank to make it "perfect", you're now pouring all that money down the drain. Oops.
Best thing to do is test your new salt water for cal/alk/mag. More than likely, assuming you're using a commerical salt mix, those numbers will be suitable for coral. So instead of fighting to "better" your water change water, just call those numbers your target numbers. You'll be able to keep those numbers consistent for quite a while just by doing normal water changes, until your corals really start to take off or your coraline algae starts to take off.
When your testing shows that your cal/alk/mag numbers are dropping and your water changes can't bring them back in line, THEN start worrying about dosing to *maintain* the original water change numbers.
Also... don't be in a hurry to add corals after the cycle. Slowly add your fish and let the tank stabilize. After a few months, then start thinking about corals.
really appreciate it. Will fully cycle this time before getting into other stuff..
