according to my Api test kit , iam at 16 dkh. Does this sound normal? ..or iam I testing wrong?.. How do I lower it? ..I tested an hr after lights came on.

It will come down on its own.

waterchange usually will help everything get back to normal

What kind of salt are you using? I am having the same issues lately. When I mix my ro/di with reef crystals it goes from 5dkh to 16-18dkh. So a water change might not be the best resolution. My LFS recommended I try instant ocean. I will be tagging along.

Iam using pre mix salt water straight from my lfs , I gotta ask what brand of salt they are using for mixing ...so it's prolly on the salt you think?

are you dosing for alk, or using any ph buffer?

No iam not dosing anything...don't know if my lfs is dosing in their water...let me check my ph...

Ph is at 8.4...

it might be the salt, but you would think that if they sell the water to other people, then other people might ask about it too. My LFS is baffled by this too. My PH is perfect, calcium 400, and dKH 16. I can only say it might be a salt issue based on my experience. I will post my new test results this weekend when I test again.

spoke with people at lfs store and they said they use oceanic salt?...has anyone had a problem with this brand?

I used to have 13-14KH whenever I did a water change as well with Instant Ocean. It would come down after a few days but after the weekly water change the cycle would start again. I have now switched to DD H2Ocean Pro salt and my parameters are much more stable. I let the water mix overnight and when I first make it I get 11KH but after letting it mix it comes down to 10KH when I actually put it in the tank. I would try other salt and see how you like it.