I build Koi ponds, usually build my own bio filters out of 100 gallon rubbermaid horse water troughs... I can take a pic if interested....

also running a UV in a pond is a lifesaver on maintence time and additive costs, check out savio pond skimmers and filters for an amazing product line, I use their bio media in my rubbermaid filter and will be using their skimmer box and filters along with my own on the larger lower pond. my buddy is a savio distributor, let me know if interested he can ship them out anywhere...