even with a lot of pods in a 30g, he'll be in trouble sooner than later. supplement him with Kent ZooPlex and live brine shrimp. and rotate in new LR every once in a while to bring in new pods.
Even if he looks fine, he may be starving. My neighbor's mandarin was fine for almost a year, but you could tell his stomach was slightly concave, and eventually she gave it to me for my tank where he has been fine since.