You can really put any brackish fish in with them, a trick to keeping a figure eight green spotted red eye topaz puffer ect from being so aggressive and outgrowing its environment is to feed them freeze dried only, never feed them live or frozen food, they will grow fast, and rather ornery towards other.....I suggest for a twenty high with one figure eight ....two rhino gobies and a dragon goby, perhaps add a knight goby as well...or maybe a jade boby and a mono or two...stay away from mollies they tend to spawn all over your tank making it a mess...if you choose a jade goby rhino gobies or a dragon goby be sure to have a soft substrate cause that's where they will be...plus with sand a dragon goby is a blast to watch eat and a master at cleaning your sand
I disagree that freeze-dried only is a good idea. It will malnourish your puffer and make him more susceptible to disease. I keep my GSP with two knight gobies and a halfbeak. They are well-fed fish and mostly just hang out like a bunch of dudes playing Halo. The key to them being happy is you. Full=happy because they aren't competing so much for food. Now, I do occassionally skip a feeding or two, but not that often. Plus I have ghost shrimp just in case he thinks its too long and he just grabs a bite on the go.
Well it works from my experience very well, it takes a lot for a puffer to be deprived to illness. But if you haven't already I would try getting your other choices added befor the puffer..good mood to avoid aggression
Feeding just freeze dried is a bad idea...will certainly negativity affect nutrition. I disagree that frozen food somehow affects aggression. A limp silverside isn't exactly the same as a wriggling feeder fish when it comes to predatory fish's reaction..I feed frozen food almost exclusively and have no adfitiona aggression problem