i might have some maroon pairing experience that i can share. i've done a few pairs since i started.
not saying this is the rule, but you should find the smallest possible fish you can find, perhaps a special order from a lfs. the latest pair i found an one-inch male (tail included) and the female is roughly 3".
you also need a safe heaven for the new fish just in case things don't work out right away. in my case i use a hermit crab cage. you don't want to add the fish directly into the big tank. you want to keep the new fish in the small cage tank and place it where the big fish can see it with good water flow. in my experience i like a picnic tank with a clear feeding window with a removable cover.
i remove the clear cover when i feed the main tank, food will flow into the cage through the window. sometimes the small fish will come out of the cage to feed. let it. if the big fish sees it and chases it, let it be for now. sometimes they might just get along right away.
if things get hairy. put the small fish back in the cage and close the cover. it usually takes 2-7 days for mine to pair up.