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  1. #1

    Koi ulcers and mouth/fin rot

    Please help, ive successfully kept koi for over 20 years but this year may be my last. Numerous koi keep suffering from ulcers and mouth/fin rot. They range from 1year old to 15 year old koi in age. My pond is approx 12000ltr with bottom drain and skimmer feeding drum filter with bio chamber with K1 media. I water change approx 1-2% everyday due to drum filter cleaning etc, over the past few weeks ive ended up treating the pond with Acriflavine 3 times and yamitsu formalite twice. No matter what I do nothing seems to prevent either the ulcers getting worse or more appearing resulting in the death of my koi. Water quality is Ammonia 0, Nitrite 0, Nitrate 10, ph 6.4, kh 4, gh hardness 7.
    Having not had to throw chemicals in before i'm very reluctant to continue with this practice.
    Any advice would be greatly received...

  2. #2
    Has the ph always been that low?

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  4. #3
    Senior Member Rank = Rokusai KiOgon's Avatar
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    Jun 2022
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    Yes, as Maddog says, what are you measuring pH with and what does your supply water measure? Is the pH reading varying during the day?

    Sounds to me like possibly a bacterial problem that's built up over the years, it seems you're doing all the right things but maybe a thorough clean out is needed and I would use Virkon to bring down the bacterial levels.

    Hope you can get on top of the problem and sort it.
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  5. #4
    Many thanks for your replies, original ph was tested on colombo 6 in 1 test strips which i'm suspecting are rubbish and totally inacurate..just retested ph with an interpet test kit and an APH kit and both come back as ph 8.5, this is the same as source from tap...
    Rather than "nuke" everything i've initially decided on a 50% water change.
    Sadly looking at our largest Chagoi though, I think this will be too late...
    It came up in conversation that bacteria or parasites in the pond could possibly become immune/resistant to Acriflavine? i was given a suggestion of trying Chloramine T for the 1st time? Thoughts please..

  6. #5
    Have you run any scrapes?

  7. #6
    Have you checked for any build up of muck any where,pipes, filter etc?

  8. #7
    As frustrating as it is i'm not in a position to do scrapes. I did ask for a microscope for fathers day but instead I got beer... ( i probably ought to invest asap)
    As for muck, theres no build up anywhere as the drum filter is clearing everything out down to 30 microns, theres a 40 watt amalgam uvc too which i'd have thought would kill at least some free floating bacteria or parasites.

  9. #8
    Have you checked in the corners of the drum for build ups? You get ulcers etc after parasites. Have they been flicking and flashing? You can't keep putting endless treatments in before you find out what your treating for.

  10. #9
    No build up in corners of drum.
    No fish have been flashing either. Last year they were flashing early in the season but ive not noticed it at all this year. Really odd as normally if parasites are bothering their skin they flash and try to rub them off but not seen it at all. Really awful as whatever the issue is it just keeps eating away at their flesh..absolutly horrid...
    Was wondering if the build up of treatments might have been corroding their slime layer away? I've noticed that when ive been pottering about with my hands in the water it kind of dries the skin of your hands up?

  11. #10
    Yes all those treatments will be having adverse effects. If its that bad,you will have to swab and get it sent off to Paula Reynolds, for suitable antibiotics. It will kill every fish in the pond, if left untreated.

  12. #11
    Quote Originally Posted by Maddog1 View Post
    Yes all those treatments will be having adverse effects. If its that bad,you will have to swab and get it sent off to Paula Reynolds, for suitable antibiotics. It will kill every fish in the pond, if left untreated.
    thankyou very much for taking the time to give me your thoughts and expertise. I'll post again with an update in due course. Thankyou. Steve

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  14. #12
    Hope you get it sorted Steve ,all the Best.

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  16. #13
    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    Hi Steve,
    Sorry to hear about your problems, sounds like a bacterial issue so I would be flushing out all pipework and do a large water change then a good dose of Virkon in.
    Sounds weird when you say the water dries out your hands,maybe the previous treatments you have put in.

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  18. #14
    A bit late to reply but hope I can offer some perspective.

    Like said above I’d flush and deep clean everything especially shower media if any. Take them all apart etc.

    Id then do a 50% WC if not done already, but refill gradually over 1-2 days without declorinator. This is to avoid dechlorinator making Virkon ineffective.

    Once drained the pond down to 50%, dose Virkon as if you have a full pond. Effectively this is a double dose. Wait for 4hrs then gradually refill the pond as above. No declorinator needed if chlorine can gas off over 1-2 days. Just don’t top up with full bore hose in one go.

    Then on day 3, repeat this process, 50% drain, double dose Virkon, then top up. Effectively you’d have then removed 75% of old water and doses Virkon twice. Fish should definitely on the mends at this temp.

    Reduce feeding to once or twice a day max. What they can finish in 1 min. You need to understand more food means more poop and more food for bacteria…

    Don’t need anything else if you haven’t scraped to confirm parasites. Just Virkon to nail bacteria first.

    I had this before and my fish all recovered with the above method.

    How often did you do water change before this happened? Need 20% weekly min. Can’t just rely on filter backwash top up.

  19. #15
    Where are you based , Steve ?

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