IMO, it is OK at pH 8.55, but if you want to lower it, aeration is the best bet. Dosing the limewater only at night may be a good choice as well.
Dosing vinegar may be a fine choice, but you need to realize there are other effects (like bacterial growth and lower O2).
This has more:
High pH: Causes and Cures
http://reefkeeping.com/issues/2005-03/rhf/index.htm