We often get the question what is a Biodrum rotator?

Well actually it is a biological filter for ponds, which creates the most perfect conditions for nitrifying bacteria. it is the best in the market for this purpose.
The concept comes from the water management industry many decades ago. It is a revolving cylinder filled with biological material that rotates which is 40% underwater and 60% above water. This ensures maximum oxygen saturation.

you may think that this is great and all but what is the need for this, especially if a moving bed or matting chamber fill the same role. But:

There have been many people who have had to wait a very long time to get their nitrite under control when starting up a koi pond.

Especially with a moving bed (combi filter). This can often be explained because the moving bed material floats around in the water and is 'bumping' into each other alot. As a result? The bacteria cannot (or very difficultly) attach itself to the material on the outside. The only material they can settle on is the inner part (which is also still in motion..).

Now most hobbyists also have large air pumps on them, which do not make the material float, but move like a jacuzzi!
This will only make it more difficult for the bacteria to settle in the moving bed material. And to make it even more difficult for him, our great friend the bacteria does not have all the oxygen he would have in the open air, because he has to do his work under the water.

But why would our bacteria prefer to live in a rotator?

* Firstly, he has the entirity of the material at his disposal, inside and outside. So there is more surface area for him to settle and multiply.

* Secondly, he has all the oxygen at his disposal to do his job, because he is constantly in contact with the outside air (That's a relief for them..!)

* Thirdly, the biological material is stationary and is not always racing past it like a race car.

In order to offer him even more choice where he can do his work the best and easiest, he will either live on the outside of the Rotator, or on the inside. There have been various tests in the water management industry that there is a difference in bacterial life in the inside of the rotator and on the outside.

Due to these perfect conditions that we offer the bacteria, it can do its job optimally and better than in, for example, a moving bed

As a result, settling (starting up) the bacteria will be easier and faster than in most moving bed filters.

In a recently published study between Rotators and various other biological filters (The Nitrification Capacity of Different Types of Biological Filters An Overview) it shows that the bacteria in a rotator can do about 5 times as much work as in moving bed filters. This means that they can break down 5x more waste with less manpower. Or that they can break down 5x more food with the same amount of biological material!

An example.
Suppose we have 100 liters of Helix 17 floating in a moving bed, or with some: racing through the water like bumper cars (jacuzzi)…! And we have 100 liters in a Rotator.

Helix 17 as a biological material has a net gross surface area to accommodate bacteria of 720m2, and a protective surface of 589m2. Hey… the difference in gross surface (inside and outside of the material) alone already shows a difference of at least 130m2! Just to clarify, that is, for example, a piece of foil laid out on the ground of 13 meters by 10 meters! (An average living room is even smaller..!) where our bacteria can house more than with a moving bed.

To stick to the example, our beloved friend the Nitrifying Bacteria has 58.9m2 at his disposal with 100 liters of helix (moving bed) and 72m2 with a Rotator (a difference of a flat piece of pond liner of 3 meters by 4.35 meters!) . So one needs almost 20% less of the material in a rotator than in a moving bed (not 100 liters but 80 liters with the same surface area)

Now the bacteria in a rotator does at least 5 times as much work as in a moving bed*. (Because he has more oxygen available there and this offers the perfect conditions to do his job)
Now if we convert it:
100 liters of helix for Moving bed = ±16 grams of feed breaking down per day
100 liters of helix for Rotator = ± 80 grams of feed breaking down per day

So with ±20 liters of Helix material, our bacteria in the Rotator can break down just as much food as 100 Liters in a moving bed! (And that too without getting out of breath and with a faster start up time!)
What type of filter would our friend choose the Nitrifying Bacteria for…??

Source:
* A COMPARATIVE ANALYSIS OF THREE BIOFILTER TYPES TREATING WASTEWATER PRODUCED IN RECIRCULATING AQUACULTURE SYSTEMS By Antar Gamble Hall

*Ammonia Removal in Selected Aquaculture Water Reuse Biofilters Gary L. Rogers. University of Hawaii, Hawaii Institute of Marine Biology, PO Box 1346, Kaneohe,
Hawaii 96744-1346, USA and 4 Stanley L. Klemetson

* The Nitrification Capacity of Different Types of Biological Filters An Overview Conference Paper November 2017

TAN values research:
Rotator 1.21g/m2/day
Trickle filter 0.64g/m2/day (=50% less efficient)
Stationary bed 0.46g/m2/day (=62% less efficient)
Moving bed 0.27g/m2/day (= 78% less efficient)