Also what size is your tank? Do you have sand or gravel? What are you feeding him?
We keep 2 in an 80g brackish water tank that we set up just for them. They are in my top 5 favorite fish. Once you've met their requirements, they really are very easy to keep.
But yes, they do need brackish not fresh to survive. We keep our specific gravity (for lack of a better explanation) the salt content, at 1.004, they can take a range from 1.003 -1.010. To fully let him thrive you will need a ssand substrate, gravel cuts them too much. They like to burrow and hide. Silk or real plants, plastic will also cut them, a decent sized tank (again, not knowing what size you keep him in), a hydrometer to measure specific gravity, reef or marine salt for salt water aquarium. Regular aquarium salt works but the kind for
SW tanks is closer to what they live in. These guys are wild caught from the brackish area in Florida, and the rest of the Southern US. It really burns my butt that stores keep and sell them as
FW. I have even gone to my
LFS with a care guide I printed for them for these guys and other brackish fish. They hand them out to customers now whenever they sell something that belongs in BW.