Hello all, I recently purchased a 30 gal tank from a friend and got it setup, due to my lack of knowledge I was way over stocked (14 goldfish & pleco). Now due to deaths and returns to LFS I am down to 5 goldfish and the pleco, 3 of which are koi but one is very tiny. I only have 1 original 26 cent goldfish left after I bought 10, all the rest are fancy. My question is this... How often should I completely drain all the water out and clean the whole aquarium. I do frequent PWCs about twice a week ranging from 25%-50%. And when I do a complete water change, what all do I clean and replace (gravel, fake plants, river rocks, decorations, etc.). Thanks all in advance.