add fresh water to brack tank?

[sanguinarydragon]

will it hurt my puffer to directly add fresh water to his brackish tank when it gets a little low?

also. he has lately picked up a habit of swiming in front of his tank when im around opening and closing his mouth. he started after i fed him a little late one day but now he does it all the time is this normal behavoir?

 

[CFC]

Do you mean to top up the water level after evapouration? If so then yes it is perfectly fine to use freshwater to top the tank up, if it is after a water change and the water is a bit low you should use brackish water or you could affect the salinity.

The puffer behaviour sounds quite normal.