High KH on new tank

Have a new reef tank which was filled 5 days ago - water tests seem ok
except for high KH which I'm not sure what to do about. It's possible too
much buffer was added by the supplier who installed my tank.

100 gallon tank with Ratz sump/trickle filter/skimmer/calc reactor. Tank
maturing with 100lbs fresh live rock and rotifers, flow rate 2000 ltrs/hours
plus additional flow off 4x1800ltr/hr power heads. Metal Halide & marine
blue tubes for lighting.

Test readings at 5.30pm today were:
Temp 26deg C
SG 1.025
PH 8.3-8.6
Total Ammonia 5.0mg/l
Nitrite 0.3mg/l
Nitrate 12.5mg/l
Oxygen 5.0mg/l
Phosphate 0.25mg/l
Carbonate Hardness  19dKH (340ppm)

Can anybody suggest what action do I need to take? ..... if any