Filter content:

Even biofilters get dirty. This ‘dirt’ can be in many forms and of many descriptions. In the most fundamental case, 'dirt' is macro debris that is carried to the biofilter from the greater pond environment. This can be leafs, seeds, acorns, fish pellets , insects and feces. These really should never get to the biofilter ( which is more accurately called a bio-reactor and not a filter at all) as every pond should have a first line of defense in the way of a skimmer basket and pre-filter. A prefilter is a concept more than a piece of equipment. The WAY your prefilter words and how efficient it is, further describes want you prefiltration approach is. You can have :
Mechanical filtration - an actual physical filtration using a permeable material that allows water to pass thru but not solids. Depending on pore size, the mechanical filter can be just a plastic cage and go right down in size to micron spacing in a paper or plastic membrane. This technique is tricky in that, if the pour size is large in order to accommodate large water flow, some material will get through. If, on the other hand, the pour size is very small to accomplish maximum protection and entrapment, the filter quickly clogs. In addition, a weak point about physical filtration of any kind, the fact that things become trapped against the force of flowing water and this tends to pulverize and liquify trapped organic debris. This then cause fines that remain in circulation and also causes an accumulation of dyes and stains within the water column itself.

A second mechanical filter type is the combined mechanical/bio design. Sand filters, bubble bead filters, stone filters, peagravel filters. OK as an old style approach but ultimately the mechanical function gets better at the expense of the biofilter function and thus requires serious maintenance or huge surface to overcome this design flaw.

Passive filtration- in many forms- cyclone filters, vortex filters, settlement chambers, baffle filters, etc. This systems tend to pull out circulating waste by employing several creative scientific/ physic’s principles. In general these are efficient and tend to avoid many of the short comings of true mechanical filters. The one weakness of these filters is that they are only as effective, in terms of the overall pond system, if what they trap is routinely removed. This often requires a substantial amount of water . But still they are easier to clean than the true mechanicals. The material they can remove are all of the macro material mentioned and additionally- do not create the pulverizing effect of the mechanical F.

So with all these designs, why do biofilters STILL get dirty?? The answer is simple. First a small percentage of particles still gets through all the above mentioned devices. Secondly many types of organics actually RE-connect and accumulate as they settle on biomedia and attract other like particles. Thirdly, The biofilter itself produces waste over time. This comes in the form of dead biofilm, dead bacteria, processed fish slime coat, process particles, dead algae content and particle formation of all this material. Often it takes the form of a green or brown paste-like muddy material. And often, this media becomes home to protozoa , worms and fungi. This material also must be removed - but not too often as the biofilter has an ecological balance of its own. It is the gross accumulation of macro material and the use of biomedia that encourages trapping that should be avoided. The slurry you may see that accumulates is to a degree, alive and will ‘live’ as long as the microbes within it stay alive. This is a layer of controlled anerobic activity.

- JR

Posted by Alan in reply to "Filter content"

Hi Jim, "Many roads lead to Rome"!

Are we looking for the shortest road, the one that is scenic, or the one that is mainly downhill and requires less expenditure of energy?

Excuse the philosopher in me but these thoughts come to me whenever filter systems and the various permutations are discussed.

I am experiencing some decent success using the prefilter "EAsy" in my settlement chamber. Although probably classed as a mechanical filter it initially works by settling out small particles of organic debris within the voids and between the static K1 media. Reportedly these small particles are not trapped as they would be by "crash effect"; rather they lose energy by the numerous changes in direction which the facets of the K1 confer and eventually settle out within the EAsy still allowing water to flow past/though the static media. Eventually there is a resistance to this flow and the media rises in its chamber signaling that it is time for a backwash. I find them ideal and a significant improvement over earlier and more expensive alternatives. They are a convenient way of controlling the heterotrophs too!

I use fluidized K1 in my second chamber and I did originally use Japanese matting in my final chamber but removed this in preference of a coarse grade matala matting as this area easily became anaerobic.
Since introducing snails and water louse into the final chamber it has stayed sweet and has not required a single cleanout. The sand like deposits which are minimal in this chamber look inert under the scope and I would like to know what these regular shaped deposits are?

These creatures have a role in the natural pond and process organic waste.

As our koi ponds only harness a small part of Mother Nature's willing work force, I try to enlist the help of any that my systems will accommodate, especially those that contribute to food webs which do not produce carbon dioxide and potentially may provide essential micro nutrients to the system.

A natural pond is self sustaining and self limiting; it utilizes plant nutrients from the water and energy from sunlight from which a whole host of food webs emanate.
Food webs exist in a natural pond such that the algae/plants use plant nutrients and ammonia from the water; these plants/algae are consumed by other creatures higher up the natural food chain such as water louse/daphnia and these are in turn eaten by fish, the waste from which feeds more algae/plants and so on. Dead plants and fish are consumed by bacteria and other reducers and the nutrients from them are returned to the pond water to enable a further cycle. Almost perfect recycling of the same materials!

In our koi ponds we do not have the plants and many of the creatures that contribute to the recycling described above. We rely mainly upon bacteria to process the waste ammonia which is continually excreted by our koi. As a consequence of relying upon bacteria to process the ammonia, carbonic acid is produced (carbon dioxide plus water = carbonic acid) and this can seriously erode the reserves of alkalinity in our ponds and drive the pH down.
As Jim so rightly points out our pond water is in a continual state of decline because we are continually adding food which needs processing in an unnatural way by bacteria, rather than the other methods which tend to recycle nutrients from the water in an array of food webs.

A fascinating subject which many koi keepers are not aware of; awareness can help us understand the need for water changes and the other maintenance chores associated with this engulfing hobby.

-Alan

Posted by James P in reply to "Filter content"

Well there is a downside to have too much life in a koi pond- namely an excess biomass uses the water and its content to the extreme and can become a burden on the system. It is also true that too large a biomass and a crash can occur and the 'sorting out' period can be both polluting and hard on the koi.
But d, you are 'old school' here. Maybe a throw back to the koi vet days when anything and everything was responsible for run away parasitic infestations and never the fault of overstocking, impossible systems, over treatments and just dumb husbandry! It is true that rats spread the black death throughout Europe once upon a time. But rats live all around us today and no one is dying from the black death. It is the dynamic of disease and parasite infestation that is responsible and not any single factor- the potential must be there- a weak fish/ excess population ( stress), bad water and an opportunistic pathogen. They all come together. Not just one.
Snails for instance, act as a stage vector and help cycle certain wild parasites but these species require other vectors and stages and can not exist in a closed system pond from generation to generation. So don't be afraid. There are worse things than worms and snails in a bioreactor. Admittedly they can be a pest around mickey mouse type low quality pond products and motors.

-JR