Just lowering and keeping your pH to something nearer 7.2 will lower the alk a good bit (I don't know exactly how much).
As to the possible negative effects of your current alkalinity, it depends on how high your calcium hardness is. If it's rather high your high alkalinity could cause calcium scaling.
The high alk will also place upward pressure on your pH.
If you do decide to lower it, follow the procedures here.
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