yeah hydrometers are worthless..
what size tank do you have?
I would just remove ~25% of the water in the tank each week and replace it with brackish water.
To make the water, just take a 1/4 cup measure and fill it about 3/4 full, and dump it in. do this once for each gallon of water.. eventually this will put you slightly under 1.008 which will be perfect.. and it doesnt even need to be perfect..