HOW MANY GALLONS IS THE TANK? IF ITS A SMALL TANK, AND YOU DONT HAVE ANY SALT WATER READY, SOME LFS SELL SALT WATER READY TO USE, THAT MIGHT BE YOUR BEST BET, BUT DONT DRAIN, ADD RODI WATER, THEN ADD SALT, YOU HAVE TO LET THE WATER MIX WITH THE SALT FOR ATLEAST 24HRS! SO IF YOU MAKE YOUR SALT WATER NOW, YOU COULD ADD IT TOMMOROW..sorry for the caps just realized it. in the meantime start doing alot of research on marine parameters. good luck!