Unless you get a "tank-raised" mandarin that eats prepared foods, DO NOT put one in a 30 gallon tank. The majority are wild caught and eat pods only. You can't put enough live rock in 30 gallons to provide enough pods to feed even one mandarin. For best success with (wild) mandarins, I suggest 75 gallons / 75 lbs LR per mandarin in a mature (6-12 months) tank. Some people have success in smaller tanks, but they are constantly buying pods to keep up with demand. This gets expensive very quickly. Price a 16oz bottle of Tisbe copepods (mandarin favorite), and you'll understand. 200-400 pods per bottle, and a single mandy will eat that in a day. I seeded my mature 125G tank and 30G refugium with well over 5000 amphipods and copepods over several months before purchasing my mandarin. I've only had him a month but as a result proper preparation, he has doubled in size.
The valentini puffer shouldn't be kept in a tank less than 30 gallons, so you're already a gallon short. Might get by with it if it's the only fish in the tank, though. You may want to consider other cute, smaller fish for the 29G. Clowns grow 3"-6" depending on which kind, so you have to think about the future. Two 6 inchers will take up a lot of real estate in a 29G.