I love Tony's #10 "letting my wife make any decision about the tank"
Find #9 to be soooo true. being cheap costs you more in the long run.
For me, the stupidest thing, well that would be bio pellets, or a variation I tried. When Bio pellets first came out they were super expensive… and were a miracle (the claim). A notion that was going around was to use rice, instead of the polymer, for the carbon source. So I took a BRS reactor, filled it half way with clean white rice. In a week, it turned to mush and had a awful smell, made my corals recess, and made the water milky. I didn’t lose anything but in hind sight – if it sounds stupid…. it probably is.