Neon Dottybacks are terrorists. They are amazing fish to have... they are active pest hunters, very hardy and dazzling fish to watch! They are VERY territorial and aggressive fish. It is difficult to add new fish after a Neon Dottyback has made its home but you can try. They usually will not tolerate similar shaped fish or fish with a majority of yellow to the body. They will hide in rocks near the substrate, and sometimes burrow as well. This being said, they also carry mouthfuls of sand around and spit it out.... mine is constantly feeding my acans my substrate!
They are very smart and very curious. When pumps are turned off they will scan every inch of the "new" area in hopes of finding a bar fight, or some food. Being a pest hunter, they can become competition for your dragonette when it comes to natural food... burning more energy, they consume a large deal more than a dragonette would.
Any other questions you have, ask. I keep a Neon in a 55g with a few of the same fish you have. I have removed my Neon and re-added him due to aggression and desire for more fish.