you still have not answered the question as to why your water is low. if your water is low due to evaporation, start a plain water drip to bring the level back up. the drip can be done with a container, air line hose and something to crimp the airline so you can control the drip. a drop or two a second should be fine. this will allow the animals to adjust. once you are back to where the level should be, then your salinity should be within acceptable levels. you then need to get a salinity tester/refractometer and check it your self. (NOW IF YOU HAVE TAKEN WATER OUT OF THE TANK THEN YOU WILL NEED TO REPLENISH WITH MAKEUP SALT WATER. ) SIMPLY PUT YOU MAKE WATER CHANGES WITH SALT WATER, AND TOP OFF MAKEUP DUE TO EVAPORATION WITH JUST PLAIN WATER AND NO SALT. LET US KNOW HOW IT GOES.