I would suggest buying bulk metro from Jehmco. You have to email or call and then you have to fill out a form of some sort for them to put on file to buying meds. It's no big deal and Jehmco, while the process seems really archaic, has been good every time I have ordered from them.
I have ordered other meds from Jack Wattley Discus (Gabe Posada) and had good experience. Be really careful buying meds if you're googling these things because you can easily end up at www.discus(dot)com and that website is to be avoided at all costs.
I can't answer about PP bath. I'm sure it has a place, but I think anyone suggesting that you do a PP bath periodically for no reason is probably a bit of a nutcase.