A while back I was given some tanks, decorations, rocks, filters and the like for free. Since it would be a while before I was going to be able to get them planted I set them up fish-only. All of the plastic plants (ugh) and everything else were absolutely filthy from blatant neglect. My solution, pop them in the dishwasher with all the settings turned to high, a healthy amount of bleach added and let it run. After that I ran another cycle with only fresh water, then one with a large amount of dechlorinator. Everything came out looking like brand new. I was amazed. The porous rock that was dirt brown from algae stains was bright white with stripes that I was not able to see before.