30G with only 50-60lbs rock? You'll starve it within six months. No matter what kind of pod population you build up, it'll never be enough in a tank that small to keep a mandarin. Even ones that eat prepared foods don't eat that much of it, they just supplement their already existing diet. Trust to advice of people around you, if you're working with less than 150lbs rock, you just shouldn't try it. Pods
are just part of the picture too, mandarins also eat tiny worms, eggs, all sorts of things that are only present in a really well established tank. Mandarins do a LOT of migrating around, they have a wide natural territory. Unlike sand sifting species, they don't just dig in at one area and ignore the rest of the tank. My spotted mandarin is ALL over the place all day long constantly canvasing my tank. I've got a very established system, with 15 gallons of fuge space, and I still feel nervous about my mandarin. Please don't purchase this fish... some things are only pretty when they're alive. A good alternative though, for beauty, small size, and activity, would be a six line wrasse. They're very colorful, active, and readily eat frozen and flake.