Gobies like a planted river-like setup and can be gorgeous, entertaining little fish. You could keep a pair in there, but they really thrive on a fully set up system... they need the biofilm so if you did go with them wait until the tank is established well to add them.
In my 20 long I have a Tetradon Schoutedeni - a freshwater puffer that can live with other fish. He has a great personality, will eat out of my fingers, and will follow me around. He loves the plants and exploring the wood branches, etc. They're a little spendy though, but a really nice, smaller "wet pet."
Then you could get other fish for more movement and activity. These puffers seem to do well with cories - there are lots of smaller species of cories that would work in a 20 long. Heck, you could probably do a pair/trio of dwarf cichlids and a Schoutedeni depending on other stock, how heavily planted, and your water change routine. They're not 100% fool proof with ALL fish, but most report good success with most. Mine nipped fins of 2 of my bichirs but hasn't touched any other fish I've kept with it, so if you go that route just keep a watchful eye.
In my 20 long I have a Tetradon Schoutedeni - a freshwater puffer that can live with other fish. He has a great personality, will eat out of my fingers, and will follow me around. He loves the plants and exploring the wood branches, etc. They're a little spendy though, but a really nice, smaller "wet pet."
Then you could get other fish for more movement and activity. These puffers seem to do well with cories - there are lots of smaller species of cories that would work in a 20 long. Heck, you could probably do a pair/trio of dwarf cichlids and a Schoutedeni depending on other stock, how heavily planted, and your water change routine. They're not 100% fool proof with ALL fish, but most report good success with most. Mine nipped fins of 2 of my bichirs but hasn't touched any other fish I've kept with it, so if you go that route just keep a watchful eye.
