So far, the only things I've found that can be acclimated to mid-level brackish is:
Bumblebee Goby (depends on exact species)
Sheepshead Minnow (Cyprinodon variegatus)
Aplocheilus Lineatus (Striped Panchax, Golden Wonder Killifish) (unfortunately too large)
Puffers are ruled out because this will be a PERMENTANTLY brackish tank, and I'm not interested in phasing it to full marine.
It will also be planted, but I know the fish will probably nibble the plants. I already raised the salinity in one of my planted tanks up to approximately 1.5 tablespoons per gallon of table salt. Many plants slowed, a couple died, but I was suprised at the number of survivors.
I wanted this tank to be a 10 gallon with an emersed area, so I'm really just looking for 1-2 nice small fish, and 4-5 fiddler crabs. Any ideas?
(btw, if anyone's interested, I'm going to try to make Caulerpa carpet the substrate, with some crypts, Crinum, and echinodorus var Vesuvious for contrast. In the emersed area, it will be mostly sand, a tiny waterfall, and saltwort planted out of the water.)