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Thread: Water Polishing

  1. #1

    Water Polishing

    Hi Folks,

    Long time lurker here.

    I have a reasonable sized pond with just 2 goldfish in it. No pumps, no filtration - I sometimes go out and scoop leaves if there are any lying on bottom. Maybe do a water change if it looks a little cloudy.

    Recently I was offered a filter cheap and took it. So I now have a filtreau 25 RDF running with an EA Varipump 20000 which seems ok, easy on electric and no maintenance. I feel like I'm about to go down a slippery slope now because I'd like the water clearer. I have the pump turned down to 50% and the float sensor at minimum which seems to be recommended for fines. Low flow and low pressure on RDF screen for best filtering. However, if I catch a container of the water from the out on the drum thereís fines in it which leaves the stream and pond slightly murky. If I look really close I can see the specs of dust floating about - very very small mind you but in the pond this means I can't see bottom.

    What can I do here? I've seen people talking about 200 litre barrels half filled with micro K1 bottom fed with a top overflow to catch these. I'm looking at knocking together one as a moving bed since I have zero biological filtration. I can acquire these barrels handy enough so thought 2 static barrels in parallel for fines and 2 in parallel for bio would keep flow low and do the trick?

    Can anyone give me a steer if this will give me the clear water I am after?


  2. #2
    Extreme Koi Member Rank = Jussai NickK-UK's Avatar
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    May 2015
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    Luxury for goldfish! Goldfish don't produce as much waste as Koi do.

    It's likely you have some tannins - these are released by decomposing bio matter (leaves, waste etc). Unfortunately tannins are very small - much smaller than the filter on the RDF.

    You could use a flocculant - that causes the particles to bind together - something like pond clear may work better. When you do this - keep stirring the pond up otherwise the settled components will simply drop to the bottom of the pond. The RDF would then catch this.

    If there's still small pieces of waste etc then the option for a small micron sock on the outlet or some floss could help. Once they're dirty dispose of the floss. The idea should be that once the pond is clear then you shouldn't get the small particles leaving the large waste to the drum. Another option is the old use of brushes in a filter chamber - these use electrostatic charge to trap the small debris.

    A bio filter pushes the nitrogen lifecycle along, the issue is that you will send up with nitrates as the final product of the nitrogen cycle. That typically uses a water change to remove. An alternative is replace the bio by anoxic filtration to remove the nitrogen.

    Start with a flocculant and a small micron sock, that you give you the space to research bio filtration in the longer term. Only thing is the fish and the current low temps probably hibernating at the bottom of the pond. So stirring up the water will disturb them.
    Eco Pond: 13,000 litres, 20K+ lph Airlifts, 1300l anoxic, Solum 16. No pump. 58W total.

  3. #3
    Thanks for the reply Nick

    I had done some leaf scooping which had stirred up a fair bit of silt, the rdf had cleared most of this out but the water was still off colour. You are probably right on the tannins and these particles seem to have settled somewhere over the last day or 2 and the water has returned to being clear. I'll take a look into a filter sock however I was trying to avoid chemicals / disposable items unless the sock can be cleaned?

    The water looks clear again which is nice so I'll have a look into the bio side of things. I did a water test and I had the slightest tint of colour indicating ammonia so it would be nice to get on top of that.




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