water essentially has no discernable pH - it is stripped of all ions (if it's de-ionized as in RO
, but even RO
water is mostly stripped). It by definition won't hurt them. In FW
, different story.
As for you salt mixture 'buffering up', it's great that you let the water mix for a week, but all you should really need to do is bring it to room temp and mix in the salt and let it run with a power head for 24 hours, and it should be ready to use. Just thought that might save you some time.
I use Instant Ocean Reef Crystals and Sea Salt on the tanks I maintain.
As for creep, you can just remove it or push it back into the sump. As long as it dissolves before getting back into the main tank, and doesn't land on any corals, it's fine. At least, that's my understanding. Correct me if I am wrong. Better to be safe and throw it away if in doubt (like if it's 1/2" thick)