Very impressive looking. The only advice that I can offer is that if you do plan on putting a light over the fuge, make sure you seal it well from splash/evaporation/salt creep somehow. I would keep a close eye on your temp the first few days as well.
Your best bet would be to use ONLY his used water when adding the live sand. You would have virtually no cycle, because the sand is not experiencing any change in water chemistry, etc. If he can spare that much water, all the better. FWIW, I found the total gallonage of this thing to be a bit less than 12 gallons when the sand was laid on the bottom similar to how yours is, maybe closer to 10.
I would add a bit of water to that existing sand and then stir it up...if you add sand first then water the water doesn't penetrate well; you end up getting air pockets underneath the top layer...then add a bit more water, then drop your live sand right on top of that clean sand. When filling the rest of the water, use a plate on top of the sand to keep it from getting entirely stirred up. You WILL get a sandstorm--it's entirely impossible not to, but it will settle in a few days and won't harm anything.
