It is still happening.
Massive amounts of competition in the pond filter market and the battle for margin is resulting in pond keepers being bombarded with techno-speak in an effort to increase sales of highly priced pond filters.
The latest product I came across prompted me to write this particular article although I've written about the subject many times.
My chemical engineering background has helped me greatly in separating fact from fiction for many pond products.
Over the last couple of years biofilters that use highly agitated water chambers containing plastic cylinders have come to the fore.
These filters are quite expensive and they do perform well but are over-engineered for most garden fish ponds.
It is also possible to get a similar effect on a DIY basis once the principles are understood.
This article attempts to explain the principles.
The reason why this type of pond filter works well The reason has very little to do with any specific component.
However it has much to do with the biological process that takes place in any filter.
These modern filters employ highly efficient biological processes made possible by agitating the biofilter media (the best known is called Kaldnes) in the circulating pond water.
By reproducing this process in any box type of filter much improved results can be obtained using almost any small bits of plastic that can be agitated.
The plastic surface is the substrate onto which bacteria cling.
They will cling to any surface.
Now here's one of the 2 major secrets ...
If the mass of water holding the Kaldnes can be agitated then the Kaldnes will remain in suspension.
Such a state of suspension is perfect for effective bio filtration of any kind.
The turbulent mixing of biomedia within a polluted body of water will allow bacteria and contaminants to come in very close proximity with each other continuously.
This means bacteria can break down toxins contained in the contaminated water (ammonia and nitrites) and have the resulting toxic chemicals removed instantly at the water interface with the substrate.
In other words old water now purified by bacteria on the substrate is flushed away and is immediately replaced by contaminated water.
This new arrival of contaminated water is then purified by the purifying bacteria before once again moving away back into the body of the agitated water mass.
This process is continuously repeated by virtue of the turbulence and agitation effect.
The contaminants in the circulating water is "bacteria food" (ammonia and nitrites dissolved in pond water and which are metabolic products of the fish).
This food is devoured quickly by hungry bacteria coming into contact with the contaminated water.
If there was no agitation the bacteria would tend to become sluggish, trapped in a static environment, while waiting for new food to come along.
The point I'm trying to make is to show that without agitation the water at the boundary of the plastic interface is essentially static or dead and the biological purification process is thus impeded.
It is not stopped in such a static bed as is the case for most pond filters, rather it is just slowed down and is thus far less efficient.
To overcome this lack of efficiency most ordinary static filters are over-sized.
Just think of how a dish washer works or a washing machine.
Leave the dinner plates or dirty clothes in a static pool of water and they never come clean.
Swish the water around and how easily the dirt is removed.
This is a simple mechanical rather than a biological process however but it illustrates the principle of boundary layer dynamics well enough.
This is what you need to know ...
All Biofilters of any kind will perform better in an agitated state.
And the Second Major Secret Is ...
Oxygen contained in circulating pond water.
Those millions and millions of purifying bacteria in any pond filter system need Oxygen, Food and a Flush to remove products of biological purification to do a good job.
Just like we do.
In a well agitated system even without extra aeration pond keepers will seemajor improvements in pond filter efficiency.
When you add extra air to keep water saturated with oxygen then the bacteria are at their most virulent.
They mop up the impurities (ammonia and nitrites) in no time at all and the "Flush" from agitation allows them to start all over again with fresh oxygen, fresh food and clean water.
These are the keys to great pond filtration.
One of the modern filters uses a venturi system to add oxygen and create agitation at the same time.
You can do the same ...
a venturi costs a couple of Dollars.