When you're first setting up your tank, you'll notice that you have the ability to accumulate both coins and Sand Dollars in FishVille. However, once you really start to play the game – buying and selling your fish and decking out your tank – you're really only dealing in coins. And that's a good thing too, because Sand Dollars are much harder to come by in the FishVille world than coins are. Because these Sand Dollars are so difficult to accumulate, it's important that you save them and spend them only when you have no other choice. But how do you know when that is?