That is a little high, which means your ALK is low and could also affect your PH. They are all three related. What kind of salt do you use? Water change is about the only way to try to stabilize everything. I use Instant ocean salt and mine stays around 500. I've heard people who use reef crystal salt say they are at around 400. It's not good to just go out and change salt so you might want to get some other feedback. Just remember stability is key in saltwater aqauriums.