ok i bought a brackish water eel sold as a fresh water eel....so i got him in the freshwater right now and need to start adding salt...i got to thinking how do i actuly do this...do i do it during water changes and id so do i only add the amount od salt to the water im putting back or enouph salt for the whol;e 20g tank i understand i should do this varry slowly only bringing it up .002 a week i need some one to help explain this process to me please