I think there are a couple of issues that cause problems for the uptake of any ideas along the line of anoxic filtration.

Here is an interesting article by Simon123 from Extreme Koi.

 Quote:

"Interesting points John. I think there are a couple of issues that cause problems for the uptake of any ideas along the line of anoxic filtration. The first is that it isn't an unboxed, plumb in and turn-on-system. You have to purchase quite a few different materials, build some kind of box/additional pool, spend lots of time cleaning cat litter and making the baskets up. I think that for a lot of people that's a step too far, they just want to be able to purchase a filtration system that they can plumb in and turn on.  

Secondly there's the herd mentality to consider. Although things constantly evolve and change in koi keeping and other hobbies the established methods of doing things become so entrenched that the initial uptake of new ideas is always a slow trickle at first. When there are proven systems out there that the majority of serious koi keepers, breeders etc. are using and have invested considerable amounts of money in, people will look at these established methods of filtration as a "no risk" option e.g., we know that they work, there is plenty of evidence for this, so why take a chance on something different which does not have the same volume of evidence to support its claims for filtration success. 

Imagine for a moment you were completely new to the world of keeping fish. You just decide on the spur of the moment to build a pond and do no research whatsoever; your knowledge of pond filtration is zero. So after a fortnight your pond is pea soup green and you can't see any of the fish you have just spent your hard earned cash on. You go to an aquatics center and they try to explain how filtration works. Now mechanical filtration is easy to get your head around even with no knowledge whatsoever. The chap in the shop shows you a sieve and you can watch the water flowing over the mesh and solid waste being captured, yes, you would understand that and be able to actually see it working: But what about biological filtration? You can look at a biological filter in action, but you can't actually see it working, converting ammonia to nitrite and then to nitrate. But we all accept that some form of plastic media, lava rock, K1 etc. in a flow of water from the pond will be a breeding ground for the bacteria that perform the nitrogen cycle. We accept this because we know this has been the predominant method of filtration for years and the results speak for themselves, it works. But would someone who didn't know this have any more trouble believing in anoxic filtration?  

What's the real difference from a novice’s point of view? In simple terms instead of flowing water through a plastic media to give the bacteria access to the ammonia in the water you are flowing water around a clay media and the negatively charged biocenosis basket attracts ammonia molecules from the positively charged water. Both mediums are breeding grounds for bacteria. A complete newbie might even favor anoxic if it is explained that when you flow water through any media it eventually becomes clogged and requires cleaning, whereas when you flow water around media in a settlement tank the clogging will not happen, rather any solid particles will settle to the bottom of the tank and will only require flushing away twice a year. 

In my opinion the accepted method of filtering a koi pond is so firmly entrenched, so proven that anyone who has a reasonable knowledge of the hobby has to fight through these perceptions of how things should be done in order to give any alternative ideas the consideration they deserve. Anyone who comes to this hobby with zero knowledge would probably be able to more easily accept the idea of anoxic filtration.

My pond now has an anoxic filter. It has only been up and running for about three weeks so like any biological filter would be it is still not mature. The bacteria need time to grow in sufficient quantities to make the system work. So as of yet I can't give you any hard evidence either way on the benefits or disadvantages of anoxic filtration. By the summer I should be in a position to start providing evidence. If it doesn't work for me I will be honest and post that information. As of yet I have had no change whatsoever in my water parameters since I turned on the pump for the anoxic filter so the only thing I can say at the moment is that it has so far had no detrimental effect on my pond water.  

The fish like it though, they have been a lot more active since the additional water flow started up, possibly due to the fact that at last I'm getting a more circular flow of water around the pond, or possibly because they can detect a change that my test kit can't, who knows? All I can say is that they seem happier. 

As to your point about blanket weed, I have had this in my pond for years. This year due to the mild winter it has started growing already. This isn't due to me installing an anoxic filter but I'm hoping a beneficial effect of the anoxic method will be a reduction or eradication of the blanket weed as the baskets remove the food source that the weed depends on. Time will tell and I'll keep posting updates on my anoxic thread on my water parameters and blanket weed situation. 

The two photos were taken today 3-22-14 before water change and cleaning of the AFS. The AFS had ‘blanketweed’ in it AKA: cyanobacteria, but these photos show none was in the main pond. The top photo shows the prefilter and though it is full of detritus, dead algae, and everything else you can think of in a dirty prefilter that hasn’t been cleaned in 4 months; still no blanketweed all over the top! You would think with all that available foodstuff for blanketweed that it would be cover in it, right?

The bottom photo shows the ponds bottom and it is still nice and clear from blanketweed, too. The BCB’s are now 25 years old in this pond.  The yellow Chagoi is 25” long (63.5cm) and this will be her third year in my pond.  She was only 13” (33cm) when I bought her.

Like you and Vince I've also read articles and blogs that seem to suggest that anoxic filtration may well help remove blanket weed in the pond but the weed seems to grow in the filters themselves. It's a mystery to me why this should happen; maybe Mankey can shed some light on this? However given a choice between a pond full of blanket weed, or a pond clear of weed but a filter that is full of it I will go with the latter. So long as the pond is clear I don't care whether there's any blanket weed in the filter box.

I'm pleased that this subject seems to be so controversial! It’s good to have an "enthusiastic" debate now and again. Wouldn't life be boring if we all had exactly the same opinion on everything?  

So I'll just make one more point and then see what reactions I have provoked, I keep seeing people saying where's the proof that it works, show me hard evidence that you can successfully filter a koi pond by anoxic filtration. So I'm asking the opposite, prove to me that it doesn't work, show me hard evidence that it is not possible to successfully filter a koi pond by anoxic filtration? Have you seen with your own eyes a pond filtered solely by anoxic filtration where the water parameters are way outside safe levels and the fish are distressed, diseased or dying?"

[Ed: Couldn’t have said it better myself, this hobbyist is already a scientist and asking the right questions with the right attitude, too.]