Thread: new to filters - what to buy

Originally Posted by mrblonde

We've just inherited several 12"-16" koi (and maybe 10 goldfish, approx 4-6" long) from an elderly relative who sadly passed. The fish are in a pretty small pond 2m x 2.5m approx, Dont know the depth. And they have a fairly old looking, basic and I'm guessing not as clean as it could be box filter. The water is not very clear.

We've rushed through digging a pond at home, in a tight space so its 3.8m x 1.5m x 1m deep. We've underlaid and lined it and filled it this weekend. Theres no rush to move the fish but we'd like to start moving them in the next few weeks.

My local water garden centre advised a Hozelock bioforce 9000, as it seemed to be the one he had most stock of. we arent hugely restricted by budget, but id like something that's fairly easy to maintain.

I didnt incorporate a bottom drain in the build, and would ideally like 2 x fountains in the pond. i know we will probably need an oxygenator and air stones.

Any advice please? Or things to avoid?

Oh, and when my pond is ready to move the fish, would moving from a small murky pond to a larger, cleaner pond cause them any health issues? i understand I have to remove all chlorine and get the levels stable, and build up good bacteria in the new filter media

3.8m x 1.5m x 1m deep = 5.51m3 or 5510 litres (assuming rectangles straight sides). If staggered or sloped sides that's a little less.

I had something basically the same as my first pond, except the deepest point was 1.2m but it had sloped/staggered sides and the bottom at the front was about 30-45cm deep. Lined etc. I also had a bioforce 9000 (it has a 6000lph pump IIRC) on there for some time. The pond had Lilly pads in etc and a veggie filter in the waterfall to add some extra bio filtration that the fish couldn't get to and destroy.

I had a number of koi in there, that grew to the point the pond was too small - basically 12-14" IIRC at the time.

I would put some pond start in - this will remove the chlorine and help stabilise the water parameters before you add fish. Note your fish pond/filter will have no biofiltration at this stage.

I found that the bf9000 was ok at best, but as soon as you have large koi, the amount of poop starts filling up the filter quite quickly in summer. It will keep the water so-so but not as clear as a drum and bio (not surprising given the price difference). I would 1/2 the 9000 with large stocks, so you will be slightly under capacity so a clean a couple of times a week may be needed to maintain the water flow rate (also you will need access to ensure the pump is cleaned out too).

I switched from that to a drum filter and the results were startling: https://www.koiforum.uk/product-revi...ndard-bio.html that shows my old pond. Also this thread where I fed the output of the bioforce 9000 into the drum to see what it would remove.. https://www.koiforum.uk/water-treatment-protein-skimmers-filtration/25225-thinking-test-pump-fed-pressure-filter.html The fish looked like they were hovering in air.