I currently have a tank with a mating pair of knight gobies, a plecostamus and a figure 8 puffer that is running quite beautifully. The figure 8 puffer is the least agressive of the brackish puffer species so can be mixed with other fish if the tank's big enough. I had some mollies and danios in my tank to start with, but the knight gobies ate them, so I'd advise keeping larger fish in if you go the knight goby route. I don't know if that helps any, but good luck!
For planting I have amazon sword and vallis growing pretty well, you could also try wysteria and java fern. If your going to keep gragon gobies go for a nice soft sand with some cavey bits for them... its true you wont see them in there full glory a lot but when you do the're such a great fish to watch
EagleC wrote: Lovely, what does he look like now ?
Alas, they do not live with me now, when I found out I was pregnant with my first child my fish room suddenly had to become a nursary However I found them a good home in Birmingham and kept in touch with the couple that took them and both are doing well still and they have a nice big tank to play in. When I had them the one in the photo was a foot long with his mate at about 8'' I do miss them =(