Newbie needs help

Hello all, just brought our first marine tank and dived straight in at the deep end! It's a secondhand tank, purchased all set up and running, corals, fish & liverock. We had a fish matinance guy move the tank for us on Monday, its all in place and looks beautiful. Problem Is when we tested all the waters yesterday we had some high readings. Matinance guy popped back today at our request and said by eye everything looks healthy and normal, told us to do little but often water changes to reduce our nitrate, here's our readings -
Salinity - 1026
Calcium - 450
Magnesium - 1400
P.H - 8.04
Ammonia - 0.00
Phosphate - 0.05
KH - 60
Nitrite - 0.08
Nitrate - 40

Is there anything else we can do to reduce the nitrate? We just went and purchased a nitrate reactor so hopefully that will help.

The tanks it a redsea reefer 450, heater/chiller at 26.5, sump skimmer and all the equipment..

Thanks in advanced for any replies :)