My friend told me about doing a top off. Is it okay if I go to the local supermarket and buy a gallon of Distilled water to do the top off? I have a 34 gallon Red Sea Max, and want to know how often people do top offs? How much water (i know not to use any salt in a top off) do you general add in a "top off"? How do you know when you have to do a top off? Most importantly, am I at risk of killing things in my tank if I use Distilled water to top off my tank? Thanks for all the help everyone's given me so far!!! Unfortunately for you guys, there's still lots more to come. LOL.