If one of them is older or much bigger, I'd say forget it. I had two C. species fairy wrasse in my 90g for a few months and it never worked out. The bigger one (C. cyanopleura), which was already established, constantly picked on the slightly smaller one (C. labouti), which I added. I thought it would stop after a while, but it never did. The labouti was never agressive, always hid, but I ended up selling the it because I felt bad. The cyanopleura was well established though and a few years old. If they're both small, then it might work out better.