The green and blue is a bit confusing with mandarins. Its a female Synchiropus splendidus (green). Its the one that you most commonly see at the LFS here. I was incorrectly told it would eat flatworms and that's why I bought it. Actually, its the S. picturatus (blue) that eats flatworms. I have one of those in my other tanks and he is fat and happy.

It sounds like you have a good home for him. He stays on the bottom or LR all of the time and I don't think your overflow should be a problem.

Gary