FWIW, yesterday i decided to use an acid bath to clean my marco rocks. after pricing the amount of vinegar i would need to do a 50/50 vinegar water mix, the muriatic acid was 1/3 the cost. so i whipped up a 10:1 mix of water and muriatic acid in a 20g rubbermaid and added the rocks. holy hell, the trashcan was soon overflowing with nasty brown bubbles and continued to do so for about an hour. i dumped the mix out and found that a good deal of my rock had disintegrated. not entire rocks, but it was definately noticeable. it made some of the more pourous rocks very brittle. if i had to do it over again, id probably use the 50/50 vinegar mix instead. the rocks did come out very clean looking though. theyre currently in a 15g freshwater soak, with two koralia 3s for water movement. they have been in there about 20 hours so far. i plan on doing a couple 100% water changes and letting them run for about 48-72 hours. there is almost no stench and the rocks look really clean. i would have liked to have kept more of the original shape though.