I want to advise you NOT to cover the entire heat pad with aluminum tape, because it will cause the pad to get much too hot and possibly short out.

The reptisafe sounds to me like mostly a waste of money. Unless you have really nasty stuff in your water, it isn't dangerous. The most common thing in tap water is chlorine, and you can remove that by just letting your water sit out in a jug or bottle for a day or two.

Other than that, it sounds like you are on the right track.

Gale