Here is where I'm different, I buy distilled water from the grocery store and mix my own. Eventually I may set up an RO sytem, but haven't yet. Cost is minimal $2.00 for 2 1/2 gallons, I do make sure to read how is distilled and most are R/O.
There is a place in Tacoma, past 512 that sells refiltered water from the Seattle Aquarium for $1.00 a gallon, you just need to add some trace elemants to it, I've used this a few times.
Be careful with the Hydrometer as they aren't always accurate, they tend to read low, which is okay as most people run their SW on the light side anyway.