Morning Bill, Jasper makes my ears bleed! LOls He is definitely filled with information.
Seriously, you name the time and the place and I'll buy!
But back to the bugs and filters. As I've mentioned, I think I was one of the first guys ( who knows if one is 'first' or a common umderstanding descents upon a group of fish geeks and then the next wave of ideas comes?) to design a fluidized bed for a commercial facility in the marine industry. It was 1981. The unit was a clear 10 foot tall cylinder. And elliptical base was fashioned over the flat floor and installed at a 45 degree angle. The water enters the cylinder under pressure and is introduced at the base via a one inch PVC pipe. The pipe volume is regulated with a hand valve. The flow of this water lifts several pounds of sand ( latter replaced with crushed coral) into suspension. It is eerie to see at first as the cylinder becomes a moving suspension of white undulating cloud in the otherwise clear water at the top of the cylinder. This becomes a super fluidized bed with hundreds and hundreds of sq feet of surface for bacteria to grow on. And most important of all, there is not trapping of fines ,or organics in general, so this is truly a nitrification reactor.
When this was tried on a koi pond, it didn't work. The reason is, the organic bombardment was so intense that a 'layer' of brown organic began building within the white undulating cloud. It was a neat trapping effect and I racked my brain trying to figure out a way to be able to remove this defined later of organic from the fluidized zone. Finally, when switching to pulverized coral in the form of a course coral sand, the layer disappeared. The reason was it was no longer nicely trapped by fine sand and became more dispersed in the column. It was becoming more of a bubble bead filter than a fluidized bed. So I moved onto 1 inch rings and air. These little guys worked well and trapped very little, but they then allowed for fines to move right thu the column. It was around this time that I met Caddock and Waddington and began adapting to the notion that a koi pond was NOT an indoor fish tank, just bigger.
Pre-filtration in koi ponds is so very important. But even with that effort, a koi pond is a closed system. The biofilm itself with adapt to biofouling. That is the ecosystem of the koi pond. IMHO. JR