01 Aug 2020
Evolution Aqua Introduces K1 Micro Media
Posted By : Guest Filed Under : Evolution Aqua
Filter media has never been so exciting! The Kaldnes 'K' series of media has been around for well over two decades, and it is widely used in aquaculture as the basis of the highly efficient biofilters required for heavily-stocked systems. Owners of Evolution Aqua’s Nexus range of pond filters will be familiar with K1 and larger K3 media, but its use in aquarium filtration has been pretty limited. With this new 'baby' version of K1, Evolution Aqua is hoping to change that, but it will also still be of interest to pond owners. In fact, the possibilities are almost endless.

What is K1 Micro?

K1 Micro is an even smaller version of standard K1, measuring approximately 6 x 6mm. The polyethylene media has a specific wheel-like shape, with a cross-shaped central portion. By shrinking the size of the media, Evolution Aqua has managed to up the surface area per unit volume, allowing for more space for bacterial colonization.

However, surface area isn’t everything — it’s what you do with it that counts — and K1 Micro has a neat feature that allows more than just bacteria to colonize it.

How does it work?

There are two main ways to use it, and combining the two can make for efficient mechanical and biological filtration.

As a static media, K1 Micro does work biologically, but its primary use in this respect is to trap solids. The media’s structure collects suspended particles, and it can then be backwashed (most effectively with air) to clean this away. This is the basis of the Nexus Koi filter’s mechanical filtration, and with a little ingenuity, this could certainly be applied to an aquarium filter.

As a moving bed biofilm reactor (MBBR), the medium’s inner surface is where the magic happens. A biofilm builds up (and bear in mind this can take some time), but it’s constantly agitated courtesy of aeration, pumped flow or even just through sitting passively in a turbulent region of a sump or filter chamber. This sloughs off excessive biofilm, making the media effectively self-cleaning if utilized in this way. Nevertheless, the protected inner sites resist sloughing to a sufficient extent to allow various communities to survive unharmed. It’s a simple yet elegant idea.


Evolution Aqua suggests that once mature and coated in sufficient biofilm, this medium is capable of harbouring denitrifying bacteria that appear to favour very specific sites on its inner surfaces. It also makes the point that the open pore structure allows for rotifers, copepods and other natural plankton populations to lurk unmolested, each piece effectively becoming a miniature refugium in the protected surface area (PSA) — now that’s amazing.

The role of communities other than microbial ones appears to be important in maintaining water quality in both pond and tank — I’m not suggesting these cryptic microfauna can’t live in or on other media (they undoubtedly will), and Evolution Aqua certainly isn’t claiming that — it’s just that it appears to have engineered an environment just right for them to proliferate in quantity with K1 Micro. You don’t need to take Evolution Aqua’s word for it, as I’ve seen some amazing photos of mature K1 Micro as proof, with hordes of motile rotifers and sessile Vorticella protozoans clearly visible.

It has promising applications for filtration in reef tanks. Whereas the use of canisters and trickle filters is now recognized as contributing to nitrates, this media could really be viable as additional filtration for invert systems if it can harbour beneficial protozoans, rotifers and other microfauna as well as denitrifying microbes.


Using the media like Kaldnes media, K1 Micro is white in colour. This may not sound like a big deal, but it allows for visual monitoring of the biofilm’s condition. If it’s nicely mature, the medium should take on a light brown colouration. A tip from Evolution Aqua is to avoid using more K1 Micro than necessary, to allow sufficient biofilm to develop on each piece for the required microbial and microfaunal communities to develop. Go overboard on the quantity and it will still perform nitrification, but it won’t reach its full potential.

You could use this medium in any number of ways, and the only limit is your imagination. Either replace or augment existing media in filters, or build your own. Experiment with various ways of moving the medium, and consider that different methods of movement (e.g. vigorous aeration versus a gentle tumbling motion) may favour different communities to develop.

Try incorporating a range of movement techniques to maximize the medium’s potential. I really think Evolution Aqua is onto something here. Being buoyant and small, this medium gets everywhere if given the chance. If using it in a sump, some form of mesh or screening is essential to keep it where it’s needed. For some applications, this won’t be a problem — it can be placed in a bead filter for pond use, for example, where it will be contained. Deceptively simple, this meticulously engineered filter medium has huge potential for tropical freshwater and marine aquariums as well as for ponds.


Vorticella micro-organisms can only at 90 degree angles in the k1 inner chamber

But if this doesn't convinced you to use k1 or k1 Micro, let me tell you the strongest weapon that any k1 has. It is the 4 hidden chambers in the center of the media. You will see the robust bio film which had grown inside. Now this is where the secret lies. Inside the 4 small chambers, lives millions of bacteria and micro-organisms of many kinds which are all beneficial to the system.

The micro-organisms in the inner chamber will eat the small particle waste. And this will ONLY happen if you use authentic k1 from Evolution Aqua made in UK, which uses raw virgin plastic that doesn't leak BPA.

Counterfeit k1 versus original k1 media

There are hundreds of different types of fake k1 media around with the world with various shapes, sizes and colours. These fake k1 media is normally made with recycled plastic by manufacturers who do not understand the science behind the original k1 media design.
  1. Counterfeit k1 media will leak BPA and although the tiny amount of BPA is not significant enough to harm your fish, the same can't be said to the poor bacteria and filter feeding micro-organisms which is supposed to grow inside the inner chamber of the media. BPA released by the the counterfeit K1 will kill all the various micro-organisms (bacteria colonies and vorticella organisms). Hence the slow flow rate and the sludge build up.
  2. There is a specific reason why original k1 media is white in colour. It is used for visual monitoring of the biofilm's condition. If it is nicely mature it should take on a light brown colouration. Use too much k1, it will still perform nitrification but not reach it's full potential because the proliferation of other filter feeding organisms such as Vorticella is discouraged.
  3. There is a misunderstanding that bacteria only grows on the surface of media. Original k1 and k1 Micro media is designed to encourage the growth of bacteria and many other micro-organims (eg Vorticella) inside the inner chambers of the media.
  4. Many fake k1 media have more than 4 inner chambers thinking it will increase the surface area. However, it discourages the growth of bacteria biofilm and many species of filter feeding micro-organisms. Original K1 and K1 Micro media have only four inner chambers. This encourages the growth of nitrifying bacteria but also Vorticella filter feeding organisms. Vorticella only seems to grow and multiply at 90 degree angles in the inner chambers of original K1 and K1 Micro media. They do not seem to grow at 30 degree or 45 degree angles. 
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