I know this is a tangent, but I just wanted to re-iterate that your mandarin will probably eventually starve in that tank unless you keep it up with copepods on a regular basis. I've had one before in a 12g and within a week or two, all of our copepods (which were breeding and thriving) were gone. It's a huge guilt trip to see a fish starving so we took him back to the LFS. Just keep an eye on him - some mandarins won't even eat frozen food, all they'll eat is pods.
I hope you get everything worked out! Again this is just my opinion coming from experience.
"we're going to need a bigger tank..."
