When my pre-formed cartridge blocks were placed in the chambers, they were clearly visible to see this blue/green material with many open squares to allow upward-flow water to pass through unrestricted.
The planks were removed at 6-month intervals to check the boxes below. We removed the cartridge blocks to see if any debris that needed removal had built up below them.
I don’t know exactly how many times I took part in this servicing process but once the planks were removed it was almost impossible to see the blue/green filter cartridge below for a layer of thick, brown dust on the top of the material.
There was only one area where the blue/green material could be seen in all these chambers and that was exactly where the water left the chamber to go out and down into the bottom of the next one.
Of course it only took minutes to siphon the brown dust away to see the blue/green below as good as new, but six months later when the planks were removed it would always be there.
In 1991 I installed my new vortex system on the main pond with a prime vortex unit linked to three more identical units complete with circular 54” diameter upward-flow cartridge blocks. The water exited each chamber by way of a central 6” tube in the centre of the cartridge block. This unit was not covered by planks and could be viewed easily.
Over a few weeks, exactly the same dust started to appear to coat the surfaces of the cartridge blocks leaving only a central area surrounding the 6” outlet where the blue/green material could be seen?
I saw this happen so many times over the years, so why didn’t I pick up on it?
Why didn’t I finally realise that the only part of the filter media being serviced by the flow of water entering the chamber were the small areas where the blue/green material could be seen?
Dust driven up by the aeration does not settle in areas where there is water flow, but it DOES settle where there is none.
I have no idea why it took me so long to finally accept all my past beliefs were hopelessly flawed and I finally admitted this publicly in 2008.
In truth, I’d wasted 27 years of my life believing my very own fairy tale.
The trouble was, by then most of the Koi enthusiasts the world over were using upward-flow boxes and they didn’t exactly take kindly for this to be pointed out to them!
Of course this must also be applied to bead filters, as they too are upward-flow boxes – albeit pressurised.