Fuges are simple to set-up. You could easily set that 55 up to be a fuge for your 125. Having a fuge on your 125 would greatly help you maintain the 125 while you are away at college. The refuge will help get rid of a lot of unwanted waste build-up and produce a ton of extra oxygen for your tank. Plus, then, it almost like you have another fish tank attached to your 125. You could run a 265 watt power compact on the 55, and then on top of doing caulerpa, chaeto, etc., you could also do corals and coral frags in the 55 as well. The only expenses in setting it up as a fuge would be getting live rock for the tank, macroalgae, drilling it, and getting a powerhead or pump to feed it water.