Wednesday, 26 March 2014

March 2014 club night with Malcolm Green

On 12 March, Malcolm Green from Koi Water Garden visited the club to provide the members with talk on pond builds and filtration. With a number of club's members away on the three day visit to Yoshikigoi in Poland the the remaining club members showed up in great numbers. This was Malcolm's first talk to the club for a couple of years and it had also been a similar timeframe since we had a guest talk on pond building and filtration.


The first part of the talk focused on his pond builds. Koi Water garden build three to four ponds a year and there was a good range of before, during and after photos to discuss.

The majority of the pond builds he had managed tended to be the popular rectangular box design. Interesting he highlighted some benefits of raised ponds that I, having had a build last year, hadn't considered but can definitely agree with.

  • Firstly, ground level ponds seem to attract all leaves as they blow across gardens whereas raised ponds only get the ones that land on the surface
  • Secondly, it's is easier to make winter covers to clips onto the outer raised walls whereas for level ponds fixing them can be a significant challenge.
  • Finally, are much easier to protect from predators and in general herons!

As an interesting nugget of knowledge, once the pond base has been dug out, Malcolm puts the bottom drain(s) in place attaches pipework back to the filter house area and then fixes them with several small concrete supports. This ensures the pipework doesn't move as the pressure from pouring in the concrete base can cause this pipe work to move / rotate.

Another useful point was that they also use plastic reinforcement filaments within the concrete mix for the base as well as the regular reinforced steel supports. The advantage of these is that provide additional strength and plastic isn't prone to rusting over time.

There was some good discussion about the finishing of the pond sides. So often fibreglassing is considered as the standard but Malcolm mentioned that the majority of his recent builds were block built with insulation and then rendered with a strong concrete mix. This render would be finished off by plasterers with a perfect smooth finish. Once drying for the 48 hours he will then paint on a coloured (normally black) aquacote epoxy finish. This reduces the need for flushing through the new system after two days to remove the toxins released by the new fibreglassing.

As a final important point, Malcolm advised to build your filter house with plenty of space so you room to make changes in the future.



In the second part of the talk Malcolm focused on pond filtration looking at the old methods to the latest techniques and equipment. The reason we need filtration is because an adult koi (20") produces as much waste as a cat every day so therefore we have to remove this from the pond water.

Firstly, there is mechanical filtration

  1. Old farms are huge settlements chambers because the solids drop out of the water. Whilst mechanically these work well, they tend to be very large and the cleaning is difficult.
  2. Going smaller there are vortexes that remove 70-80% of waste. By adding filter brushes this improves solid removal because as the water flows through it catches the particles. They do need cleaning every 2-3 weeks.
  3. More modern pre-filter sieves work well and can remove solids down to between 100-300 microns. They tend to be smaller and from personal experience they needs a quick flush once a week. They do need a pump to drive the pond water through but they work well.
  4. Lastly is the use of belt / drum filters. These can be thought of as a rotating sieve and can remove waste down to 60microns. Their unique auto cleaning mechanism is triggered when the water level inside the drum differs from that outside the chamber (indicating blockages).


Secondly, there is biological filtration

  1. As a key point, the better your mechanical filtration is at removing waste the smaller you biological filter need to be
  2. Coal is carbon and that will grow good biomass so therefore is a good form of media still used in Japan.
  3. The next types of media for the biological section are japanese matting and Alfa grog. These work very well because they are porous and therefore support good bacteria growth.
  4. The polypropylene media such as K1 are great due to the larger surface area and are used in the popular Eazypods and Nexus 210 / 310 filters.
  5. Ceramic media - matures quickly but as a downside it strips your KH over time. Your need to carefully monitor KH.
  6. It must also be considered that the walls and the floor of the pond are also part of the biological media.
  7. In addition to standard biological media filters the use of a protein skimmer will remove very fine (micro) dirt. This is achieved by the small particles of waste / protein attaching to the bubbles being generated within these filters. This foam will then be separated and removed to waste. These are widely used in commercial fish farming because fry do not grow well in high levels of nitrates.


The third and final stage is bacterial filtration

  1. You can buy dip slides to indicate bacteria loading and these are available from Paula Reynolds.
  2. Chemically disinfect the pond with a product similar to Virkon. IT is safe to use the full dose. This will last for five days in the water. At the start of the year it is advised to give the pond two full treatments and half on the third week.
  3. You should always use a disinfectant product when adding new koi because they can cross infect.
  4. In addition to the above, the standard housekeeping procedures of 10% water changes every week and ensuring your stocking levels are low will help reduce the impact / chance of bacterial issues.


Many thanks from all the members at Kangei, this was another excellent club night.



Next month (Wednesday 09 April 2014 at 19:45) we have Kevin Ellis (well regarded) koi hobbyist providing us with a talk.



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