Try reading thru this hole book,(free) the patent holder dr. Novak (American) is a sientist but also a hoby koi enthusiast. There is a lot off controversy to his filter system (anoxic)but it seems most off his critics manufactur or distribut(sell) competing technology for big money, so a cheap DIY solution is bad for buisnis?
He coresponds with happy Koi breders around the world, that have adopted this way off filtering the koi pond.
The site is indipendent and have made the anoxic filter solution understandable (language) to hobyists. Dr. Novak still get prety heavy beating on a lot off koi forums, by "disbelivers" However the number off people sucsesfully using anoxic filtration is increasing in the US as well. Seems it's hard to become a "profet" in your own country.
Iff you dont belive in the method after reading the book I think maybe, 1. generation ERIC (Endless River In Concrete)by Waddy is a good an cheap($) route to prosue if your handy(DIY), do to the simplisity off the set up.
