Hi Frank, apologies but I'm not used to navigating this forum.
Here are my own personal views regarding Drum Filters in general.
Drum Filters have now been used in Koi pond applications for over a decade.
Publicity would have us all believe that they are the most efficient mechanical filter stage possible - because the same publicity ‘infers’ that NO mechanical waste can pass through.
However, no manufacturer to date has ever ‘made this statement openly’ and to date it has only been inferred.
Man-made fishponds are often very filthy bodies of water - especially on the pond bases where most of the waste matter ends up.
This waste matter varies in all manner of sizes from large leaves right down to the finest of dust possible and here’s an example –
See ‘0’ jpeg here.
Regarding this ‘finest of dust possible’ – the only medium I know of that can remove all this for certain (100% guaranteed) is Diatomaceous Earth.
I have witnessed this medium used as a mechanical barrier many years ago, and after allowing pond water to pass through for only a few minutes, it even prevents water from passing through!
In short and in my opinion, if water can pass through a Drum Filter and then into the biological stage - then so can dust, irrespective of the micron size of the screen.
In fact I know of NO mechanical filter stage used on Koi ponds that can prevent some debris from passing through.
Many also consider that if no waste passes through into the biological stage then the biological stage will always remain to be clean.
Alas, this is only a myth, because the bacteria present in very efficient biological stages are constantly manufacturing their own waste products in quantity and these also need removing from the biological stage with regularity.
This is a shot of the fine ‘sand grit’ that’s manufactured only in the biological stages of my Eric filters.
See ‘1’ jpeg here.
Now the question is – ‘Do we really need to install another Drum Filter to be placed ‘after’ the biological stage’?
Publicity also states that Drum Filters are maintenance-free, but is any motorised unit with moving parts ever really maintenance-free?
I have not yet mentioned purchase prices because keeping Koi is a costly hobby and many are quite prepared to pay the price for perfection.
However, ‘compromise’ is not exactly ‘perfection’ is it?
And this is also the time when purchase prices need to be seriously considered.
To summarise, Drum Filters are doubtlessly far superior to Sieves and ‘The Answer’ but they are all simply perforated stainless steel screens and all will need to handle and cope with Bio Film.
For my part I’m staying well away from Drum Filters and will continue to stand by my Brush Box that many tell me is ‘Old Fashioned’.
See ‘2’ jpeg here.
I have many reasons for saying this, such as –
The tethered brushes TRAP 95% of the debris and also RELEASE 95% of the debris. (Several others do a good job in trapping the debris but few like to release it.)
It is impossible to ‘block’ my brush boxes.
The filters themselves only hold a small volume of water and that water is flushed to waste on a daily basis - in seconds.
If there IS 5% of debris in the biological stage that also gets flushed to waste daily.
Brushes last indefinitely.
There are no moving parts in my brush boxes.
There are no running costs involved with my brush boxes.
Even the very latest three-stage brush boxes only cost £200.00!
See '3' jpeg here.
If you read my website
www.ericpondfilters.com you’ll see that the main reason I had in making my filters was that I honestly believe they will not allow any NEW instances of shimi and hikui to take place.
Some of my filters have now been running ponds for 42 months and to date, there are NO new instances of these problems.
Thanks for reading and regards.
Waddy.