I don't know of the facts you're looking for, but I did find a useful solution when using clear pots. mine are made from gallon jugs in ebb and flow, so I was worried about having any kind of paint or metal in the pots touching the nute water, and plastic usually doesn't block enough light. then I found landscape fabric. the stuff used to block weaks. it breathes well and blocks almost all the light. I line my pots with that. my pepper plants don't have that fabric or anything else in it. the pots are clear and you can see the roots. they are white and I haven't had any problems in the last few months, but doesn't mean he wont have problems. I might have trouble with it in the future if I didn't start using the black fabric. if your buddy uses H2O2, that might help prevent any problems.