No i completely disagree dont dissolve it first. Pouring the grains is the best thing to do. It will slowly release the salt as it dissolves. If you dissolve it before hand, they are getting a fast rush of electrolytes into the tank. Always pour it directly in.
""""won't they try to eat it if you just spoon it in? I thought I read somewhere that salt can cause burns on fish if not desolved but I notice at fish stores tehy just put a cup filled with salt in the tank and let it sit like that. Why do they do that?"""""
not at all, fish are not that retarded, if it is burning their mouths, they won't nibble at it. Just like if they see poop floating around and nibble at it, they notice it tatses bad and discard it, they don't keep trying to eat it. Also I've never had a fish nibble at the salt I throw in once it touches the bottom.