???High alkalinity???

16 dKH in a reef tank? With what corals? Or, is it a FO / FOWLR?

It could certainly be bad if you're talking about a reef tank, because it's likely that with a KH so high the calcium levels are pretty low.
 
The calcium levels are fine, but there is no coral in the tank yet. Im working on getting ready for coral so I want to get everything %100 first. I'm doing a %30 water change today and I will let you know the new levels later.
 
If you can get the KH back down closer to 12 dKH, that would be better before adding any corals. I accidentally got my alkalinity up to 13 dKH last week, but I try to keep it around 9 - 10 dKH.

Did you accidentally add too much alkalinity buffer? Is there some other cause that you know of for the overly high alkalinity? Using tap water or RO - RO/DI?
 
11.9 dKH is fine. I wouldn't worry about getting it any lower... once you have some corals they'll help bring it down as they consume it (mainly any LPS or SPS you might have). But, being around 11 dKH is certainly not bad at all and a good place to be.

BTW, what brand of test kit are you using to get a reading of as precise as 11.9 dKH?
 
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