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My main pond is 5000 litres and there’s 17 medium sized fish in there. Ranging between 30 and 40 cm. Roughly the same as your 7 in 2000. In mine there’s too many really but in my view it comes down to three main factors: 1. maintaining carbonate levels - smaller pond relative to weight of fish means less absolute level of CO3 buffer so you need to be watching carbonate hardness closely in summer and must use a chalk buffer or do massive water changes to maintain it. 2. The filter needs to be big enough for the fish not the pond. This means when over stocked your filter needs to be big relative to the size of pond and plenty of circulation in the pond using air. 3. Diseases will spread more quickly, and as it is outdoors you can’t stop diseases being introduced, so from April you need to vigilant and treating promptly. I get multiple breakouts every year. Hope that’s helpful, I’m sure there are additional things I’ve missed. I think your koi centre is giving you great advice

Thanks. I’ve found that in order to get a decent sample the sharp edge of the slide works well but given how fish thrash around I’d much prefer to sedate a bit to avoid them hurting themselves on it. However I think what you are suggesting would make it a lot quicker and means you can do it at lower temperatures but I think then it’s a question of skill!

It’s a good suggestion and I did use bicarbonate of soda in one of my experiments keeping my filter going during the winter in a barrel in the garage, although not sure I mentioned it in the video. It does dissolve more easily than calcium carbonate, I wonder if there are any drawbacks as it seems less used here in the UK? I was a bit concerned about a build up of sodium in the water compared to calcium. Thanks for sharing

From a quick google it looks like 9-10 is the equilibrium for calcium carbonate in excess which would be too high for koi. However I would expect that a pond would remain some way off this level with a lower pH even if there’s plenty of oyster shells as I don’t think oyster shells are particularly fast at offering up their calcium carbonate due to a lower surface area compared to powdered chalk. I know from previous experiments that you can get the KH to over 20 degrees with an excess of chalk powder, I didn’t measure the pH though. You’d need a massive dose to do this in a pond though, which I wouldn’t advise!

Yes but there will be benneficial to stay on the positive side of kh buffering. The unansvered question is. Will there be exess buffering with a large amount of crushed oystershells. I have put in a 10kg bag of crushed shells in 40-50m3 and i messured 1 degree of kh. Eirik

Due to a mistaken choice of cat litter (do not use Catsan) in some anoxic baskets I was using, the lime caused a huge increase in GH and pH. It topped out at 36GH before I took them out and remade them with Moler Clay (Kittyfriend). The fish were unconcerned by that and by me doing a daily run through of 10% until I was down at GH10 and no longer adding vinegar to maintain a decent pH. I have lots of Oyster Shells in the side ponds in my system. They don't dissolve very much in my water which sits just short of PH8 but they do provide some more growing space for beneficial bacteria and if I fail to notice a deteriorating KH and falling pH, they will dissolve more quickly and hopefully give me a better chance of avoiding a catastrophe.

Hi. What about trickle in trickle out?

It’s a great question. I’ve really struggled to think of any experiment to do with nitrates as the test kits are very inaccurate and quite temperamental in my experience. Also I’ve not tended to have any issue with nitrates as plants, algae and water changes seem to keep it in check. I’ve found maintaining sufficient KH to be the more pressing constraint meaning I do plenty of water changes in managing that.

Hi - not sure what you mean by KO? Did you mean KH? Having learned a bit since doing this experiment I’m now inclined to think the reason the higher ammonia levels didn’t work as fast was because the KH was all used up. I’d need to re run the experiment with a load of calcium buffer but my gut feel is that this would probably mean higher levels of ammonia could be used without issues.

That sounds really interesting. What specific product do you use? I might test it but it would be essential to know the exact product to know it’s safe with fish! Thanks

It’s an interesting idea - you could either isolate it from the pond and heat it which is effectively what I did, or have some sort of heat exchanger to cool the water down as it leaves the filter, and heat the water up as it enters- but that would pretty elaborate!

Yes definitely but you need to bear in mind a couple of key things. Whilst you will speed up the growth of the bacteria in the heated aquarium, once they are cooled down in the pond they will work much more slowly than they did on the aquarium so it will still take a long time to build up the necessary level of bacteria ready for the pond - but it will certainly help, particularly over winter where they would otherwise be dormant or dying back. You will need to do water changes or alternatively regularly add calcium carbonate or sodium bicarbonate to give the bacteria enough carbonate to feed their growth as well as ammonia. From my own experience I’d say you’d need grow them to for about 2-3 months to be making a noticeable impact. I found even having kept my established bacteria warm and fed over winter I still had a nitrite pickup in May time - koi eat obscene amounts of food!

Hi - I’ve read about the concept but haven’t put into practice. Sounds interesting though. May be one for a future experiment!

Hi - that’s a pretty big operation you’ve got going on there. At face value the experiment I ran would suggest 11,000 litres of k3 - which sounds excessive. However something that I’ve subsequently been working on is the scope for food to be incorporated into the fish and so food consumed doesn’t equal waste produced. From my wider reading this can be as little as 10% in high growth species such as salmon. So if you are feeding at that rate and the fish are all growing strongly, as opposed to simply maintaining their size, the amount of k3 needed could be as little as 1,100litres. Would need to be very heavily arrested too. As it sounds like a professional arrangement you have I would suggest going with k1 which is twice as effective per volume and also consider using other high surface media such as siporax along side.

Interestingly the kujaku, which grew about 2cm has continued to grow at a pace since I put it in the main pond, at least 2cm per month since and the temp has been 18/19. I can imagine that Increasing temp and pure growth food could deliver 4-5cms. Good work on getting that sort of success with you fish. Thanks

Yes very fair point

Hi - the right treatment depends on knowing exactly what you are treating. I haven’t used methylene blue for many years and that was on a tropical tank to treat white spot which it was very effective at. I’m not sure why it isn’t talked about in ponds much but I imagine it’s that malachite and formalin is more effective against a wider range of parasites. Methylene blue also has a habit of being absorbed into rocks etc which then turn blue. PP is one of my favourite treatments that I use at least twice in spring and twice in autumn as a preventative. It has the nice feature of leaving the water crystal clear but like most treatments isn’t kind to the biological filter. Formalin and malachite is more effective than PP for things like even though both are said to work. Be very careful with your dosing of PP in particular. I don’t use at concentrations of more than 2mg /l and generally use 1.5mg/l

​@@thekoilab3944 i keep only snakeheads, and i regularly try to pair them up - which results in A LOT of pretty gnarly injuries and wounds.... sometimes the wounds are ripped scales (light injury), sometimes its "white" wounds (moderate injury), sometimes its "red" wounds (severe injury), and also open wounds and lacerations. torn fins are a guarantee. after 12 hours, i would take the fish and hand-paint them entirely blue with a brush and MB, 3 times. i let them swim in a shallow, MB-tainted, tub of aquarium water, after each going-over (about 30 seconds of swimming). (i then rinse them off with clean aquarium water, twice, and then re-release them back into the tank.) someone whos more experienced in this mentioned PP is better for this? when in fact, my research shows that MB is the best. thanks for helping a fellow aquarist out. im not ever happy that these goons tear each other up; it breaks my heart. but thats how they pair up in the wild anyways...