I did a partial water change in my problematic 25 gal today. I'm using coral reef crystals this salt was baught 7 years ago but the five gallon pail was never opened. salt never goes bad if sealed . I haul this stuff for a living. Well it says 2 cups per 5 gals it took 3 cups to get salinity to between 10.24 and 10.25 what caused this same problem last time I mixed it . I mix it in 2 5gal pails and run a heater and power head in both pails at least 1/2 a day. Whats the problem ?