Drew, always try with one fish first, I think it will be better, you can buy a pair, but since you already got one, just see how it goes, give and take about a month, after that you can start adding a new fish. By thumbs rule, it's supposed to be 1 fish per month, but I think if you introduced 2 together since ur tank is huge, it should be alright.
Remember, keep checking the water parameters make sure that your tank is good.