Get a ten gallon aquarium, and look for an auto top off setup! It's perfect for when you don't feel like dealing with the tank for a few days. For the tangs, get a veggie clip and put some EDOMAE brand seaweed from H-E-B in it. I fold my pieces into a "paper football" and then clip it in. My tangs attack it with great ferocity! The fold method helps to keep it intact. They should be fine as long as you feed them right before you leave and right after you get back. We go to the coast alot, and we are gone from the tank for a few days at a time. I let my mother go ONCE to feed my fish, and she poured a weeks worth of food in at once. THENNNNNN she decided to top the tank off. She had no idea a sump resided below, at least until the carpet was wet.