I have a similar situation. I have a tank with two young clowns, two smaller firefish, and a decent sized Lawnmower blenny. I wanted to get a neon goby, just for a color besides orange and white. I got the tank from my Chemisty teacher when she left. I helped her stock it over a year ago, and watched her kill them all off by overstocking it by a couple of mandarins... I just don't want to watch my nice tank fall apart.