I've got a problem. I built a deck that overhangs and wraps around a koi pond. It's wonderful but there's a a major maintenance problem of not being able to use harsh chemicals (alkaloid lye) to strip the deck because of the fish. Any washing off of chemicals (deck stripper) is bound to get into the water, and lets just assume that covering the pond isn't going to work. Now, there are environmentally friendly deck stain removers, such as BioWash, but do these guys actually work and are they "fish friendly"? I'd hate to chance killing prize koi.