The refractometer on eBay will work fine. Distilled water will work also. The solution is best to calibrate IMO
. Sorry I wasn't in here earlier I passed out.
Also yea I'm sure the guy at your LFS
is correct however you should have the equipment to test your salinity yourself. A hydrometer isn't accurate and why play the game? He's 2 points higher so you should be 2 points lower.
Next week maybe yours is 3 points low his is 1 point, you get my point right?
Accuracy is key. I wouldn't wanna play that game once your corals, inverts are in and you add more fish.