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Mechanical filtration capable of removing fines.


Mechanical filtration has long been a problem, needing large diameter vortex's to get reasonable settlement, but these still let a fair amount of fines through to the biological stages of the filtration system. These large settlement vortex's take up a lot of valuable space, which if made smaller could allow this space to be used for more biological filtration. So smaller has been my goal, but this smaller system much be capable of catching all the fines which normally coat the biological media and spoil the viewing of the pond with constant minute particles floating in the water column.

In June 2003 I was asked by a gentleman who had been given my number if I could make the water clear in his pond system by August for his daughter wedding. I went to view these ponds and access the situation. There were 4 ponds, all joined by moats which circled the house, total volume well in excess of 50,000 gallons. The water was green, this was no problem with a few UV's fitted, but the biggest headache was the suspended fines. These ponds have no filtration and had not been touched in 6 years. The koi were large and many in number. They constantly stirred the bottom and kept the water murky.

So I went home and designed a means of trapping the fines. Small footprint was a must, as any filter had to be hidden within the bushes of the garden which was beautifully landscaped. I went home and made 4 of my smallest size vortex's, 24" diameter. To each of these a grid was fitted over the outlet drain, inlet water was elbowed down to the bottom, as I in this situation I was not interested in settlement, just trapping the fines. Outlet water was to be taken from top center.

Into each of these 50 litres of Kaldnes K1 was added and this was capped off with a disk of Japanese matting. Water pumped into the bottom, the fines are trapped by the Kaldnes and the clean water flows out through the top.

These were installed on the ponds and left running for 24 hours before my return. I was amazed at what was captured.

Below are two photos, the first is of the water in the filter once stirred up the other is after cleaning and rinsing.


This is what the discharge water looked like!


Having been so impressed by the outcome of this style of trapping the waste, within weeks I was modifying my settlement design at home.

I have redesigned the layout, as cleaning was a little messy and involved getting ones hands wet!! Now the whole process takes only a couple of minutes and give me clarity to a level I have never experienced before.

I use the same 24" vortex, but now designed exactly as my agitated Kaldnes chambers. A grid to stop the Kaldnes washing away when draining, a slotted pipe for water exit and a drilled PVC pipe ring for cleaning the media. Less media is now used, this allows a certain amount natural settlement for heavy solids. Using this sizes vortex it is possible to gravity feed 2,000 gallons an hour through the Kaldness, using a conventional vortex would it would need to be about 48" diameter to get reasonable settlement and this would still allow a large amount of fines through.

Running this system is simple, when the pump is start, the Kaldness starts to clump together around the exit pipe, the water flows through the Kaldnes media which is now tightly packed, it traps the fish waste, large and small.

To clean the media is easy, just shut the valves on inlet and exit sides. Open the drain valve a little and drop the water level to just below the slots in the exit pipe, turn on the air and let the media agitate for a few seconds and then open the drain valve releasing the rest of the water. Repeat this process two more times, this gives the bottom drain line a good flush and the constant agitation cleans the media spotless.

Word of caution.

In my view this style of trapping the waste is not for the 'occasional' filter cleaner, as with Bubblebead filters this type of filter needs frequent cleaning, every day, less the trapped waste will go anaerobic and encourage gram negative bacteria, this is the type of bacteria we do not want in our systems.

I have found using these trapping filters i can judge the health of my koi from the smell of the waste while agitating the media when cleaning, if the smell is fowl it means the koi have a digestion problem and food needs cutting back, if the smell is sweet, like fresh compost, all is well. Left longer than a day and it will always smell fowl!!

I use this, ONLY as mechanical filtration, though the media will coat with bacteria it is not counted as any part of my biological filtration.   Below is a photo of the media after running for more than a year, coated with bacteria, giving it a fawn colour, but harboring NO waste after flushing.