Sick Koi

Sick Koi but good water parameters in outdoor Koi Pond??


I’m currently babysitting my parents’ outdoor koi pond and will be doing so for about 2 weeks. It’s quite a large pond (10,000 gallons and spans half of our backyard). We have several large koi (length of adult forearm) and several smaller goldfish (length of adult palm) and based on the number of fish, the pond may be overstocked. The outdoor temperature in Vancouver has been quite variable this summer (16 – 32 degrees Celcius. Low-mid 20’s this week but the temperature was up to 30 degrees over the last 2 weeks). For some reason the pond is losing about 4 inches of water each day so we refill the pond with a bit of fresh water each day (like a 5% daily partial water change!). My parents have had this pond for about 5 years.

At first glace, the fish look relatively healthy (full scales/fins) but there are always a few fish in the pond that have finrot, sores on the body or strange growths. Some fish have had raised scales, pineconing and died not having released their eggs. The fish have been exposed to salt and antibiotics many times. Sometimes the treatment works, but on average about 1 fish dies each month and my parents replace them. At the moment, one very large fish currently has sores on one side, some raised scales and prefers to swim at the bottom of the pond and doesn’t seem interested in food. Another strange observation: when I fed the fish this morning, I noticed that 3 smaller fish appeared to be chewing/biting another small fish of similar size in a corner of the pond. When I threw food at them, all of them swam away. What does this mean??

Seeing that there are always ill fish, I assumed that there must be problems with the water quality. However, when I tested the water parameters of a sample of pond water today, they seemed ok:
Ammonia: 0-0.1
Nitrite: 0-0.1
Nitrate: 5-10
pH: 7.2-7.4
KH: 10
GH: 20
Phosphate: 1

I came across your site and thought that the garlic may help. My parents usually feed Hikari pellets twice a day, so over the last 2 days I have been feeding a mix of presoaked pellets and cooked peas but I think only the smaller fish were able to see the crumbled peas because the large koi swam right through the small bits.

I have attached some images of the pond. Please let me know if you have any ideas



By | 2019-04-01T10:25:45-05:00 July 12th, 2017|Categories: Goldfish Koi Health Issues|

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  1. emme April 8, 2018 at 8:06 pm

    My dad replied:

    “True story : The fish has been covered with the green algae on the dorsal fin a few months. I was trying to catch the fish a long tome ago but it was so hard to catch it. Last a few days ago, the fish started coming up looking for food and swimming very fast. A very healthy fish no sign of any illness apart from the green algae on the dorsal fin. I happened to be just lucky to catch it up with a net when it came approaching me for food. The fin was already eroding . The green algae were rubbed off with brush soaked with salt paste. I think it was too a big shock for the fish to bear when I held it without first putting it to sleep. Very stressful it could be ! Imagine when a guy was having operation without anaesthesia! Secondly, the water was still cold so the chill and stress further suppressed the immune system. Although the day when I put the fish back it stilled looked ok, but the next 1 to 2 days after, it never recovered . I should probably treated the fish when it is warmer.”

    • Venus April 9, 2018 at 7:55 am

      It’s entirely possible. I have just recently instructed oral digestive health remedy as a preventative treatment on a fish that was exhibiting good health, and it died soon after. It’s tank mate was having floating issues, and was treated successfully. It was quite a shock for everyone involved. The fish was blind, and 13 to 14 yrs old. I’ll be writing an article on the topic soon, however, a healthy fish is easily able to endure being handled. The fish was obviously in poor health. It doesn’t take much to push a sick fish over the edge, and shock is just one way of pushing. In some cases, the fish has to be handled; it’s catch 22 I guess

      My thought is, the fish I recommended treating wouldn’t have lived much longer, and the same is probably true for your fish, so don’t go beating yourself up. Let’s both just learn from the experience. In the future, I won’t recommend handling a old fish unless it’s life depends on it; lesson learned

  2. Venus April 2, 2018 at 5:55 am

    From what I’ve learned, the green is a form of bacterial infection, something similar to, if not impetigo. Some say it spreads to other fish, but in these cases the water is unhealthy. This is a rare condition. I’ve seen two other cases, each located on the body, and no real sign of infection; just the green coloration. In both cases, the fish were just fine. It would be interesting to know if the green was short term, but that was a while back

    Clamped fins indicate either ammonia poisoning or high KH levels as you know, but I just wonder if the fin wasn’t clamped, but limp. The dorsal fin collapses when a fish is really sick. Healthy fish have erect fins, although you’ll see the fin move up and down as the fish swims about. It might be hard to tell with a Koi; most having short fins, whereas goldfish have larger dorsal fins, making it more obvious. There are breeds of goldfish with no dorsal fins; very strange

    I’m not sure I would recommend rubbing salt directly onto a wound of a fish. It’s possible the infection entered the blood stream, killing the fish, but it’s also possible the fish died from salt poisoning. If infection could enter the blood stream via a wound, so could the salt. A salt bath would have been just as effective, and safe. Freshwater fish have a very strange reaction to salt. The salt dip; more extreme than a bath, if done properly, causes the fish to pass out. Once the fish is placed in freshwater, it revives instantly. It has to do with the chloride in salt, and is probably related only to the salt coming into contact with the gills. A dip isn’t long enough to allow much salt to enter the blood stream

    No matter; just theorizing really. We’ll never know the direct cause. Another member just lost a fish after treating with my Digestive Health therapy. One fish was floating due to being constipated, so we treated that fish, and it improved asap. The second fish was treated as a preventative measure, and it died soon after treatment. It thrashed around, and went into a panic. Both fish are 13 to 14 yrs old. I would think the fish died of a heartache, so you see? You never know. Maybe the fish died of something completely different than what is obvious

    Young people can have strokes and heartaches, and so can young fish. In the future, I won’t recommend handling an older fish unless it’s necessary. Goldfish and Koi are prey fish, and they go into shock easily; stress can kill. I feel another article coming on

    Strange reaction to salt. I would say the fin was eaten up by the bad bacteria, and the tissue was pretty much destroyed before your dad rubbed the salt on.

    It doesn’t surprise me; the loss of a few fish this winter. The fish were in rough shape, even though we started buffering the water before winter hit, they didn’t have enough time to regain good health. Winter is hard on fish, but this isn’t necessarily a bad thing. Having a large pond with a large school is very different than having a few fish in an aquarium. It’s not easy to spot something off until it’s too late

    I’ve always thought of winter as Mother Nature’s way of culling the weaker fish from the school. The end result is a healthier school

    We’re almost done with Old man winter, so hang in there. Once the water has warmed, look the fish over, and see if any others are looking poorly. It’s not practical to treat the entire pond with a remedy, but we could bathe the fish in a remedy. Hopefully, it won’t be necessary

  3. emme April 2, 2018 at 12:54 am

    Hi Venus,

    The outdoor temperature is still 4-11 degrees celcius. We have odd days thats are 14-15 degrees but they quickly drop back to colder temperatures so we still have not fed the koi.
    Currently ammonia/nitrite/nitrate=0, KH=100, GH=100, pH=8.2.
    We have lost a few koi this winter. The most recent one occured a few days ago. The dorsal fin had a strange green growth on it. My dad rubbed salt paste (aquarium salt+pond water) on to the dorsal fin but a few days later, that fish died, with fins clamped and dorsal fin shredded/gone. Do you think it was a bacterial infection?

  4. Venus January 15, 2018 at 6:47 am

    Start feeding one light meal a day at 54f. You would feed food high in roughage, easy to digest, such as peas, blanched green leaf lettuce or fresh spinach, and feed lightly, according to the water temps, not the temps of the air. When water temps reach 64f, you could increase feedings and add normal food

    Although they can eat algae if they’re hungry, you don’t want them eating it all

    With such a large body of water, the temps will be relatively consistent, whehter they’re rising or falling

  5. emme January 14, 2018 at 6:24 pm

    Sounds good! I’ll keep maintaining the water parameters. Will keep you posted 🙂

    Btw, when Spring comes and we start feeding again, is there a way to feed properly to ease the fish/good bugs out of dormancy? Or does the cycle and everything just work again with normal feeding?

  6. Venus January 14, 2018 at 8:26 am

    No, don’t use heaters. This just confuses the course of nature, which the fish are a part of. The school will be healthier for experiencing a natural winter.

    It’s likely the fish has some issue, but if it’s alert, I don’t think it’s serious enough to keep it from surviving. My guess is, the swim bladder is doesn’t have enough gas in it to keep the fish upright; let’s hope that’s all it is. It’s tricky, the coming of winter. The fish needs to have some waste in it’s track to keep gas in the bladder. If the digestive tract slows when the tract is too full, the fish may be unable to sink, and be exposed to water that’s too cold at the surface. If the tract slows, and no waste is in the tract, the fish may not have the boyancy it needs to stay upright

    Your pond is large enough that the water will warm and chill gradually, making it easier on the fish. A lot of fish will eat in cold water temps 40f, but this doesn’t mean we should feed them. If algae is available, and they’re hungry, this is all they need

    I wouldn’t worry about the fish. If it makes it through the winter, and it probably will, we’ll see if there are any health issues that need attention. I think you’ll be amazed at the health of the fish when Spring comes. You’re doing a great job with them

  7. emme January 13, 2018 at 12:10 pm

    Hi Venus,

    There are still 3 pumps on in addition to the waterfall running. There is a bit of algae in the pond. Nothing is frozen at the moment as the temperatures are consistently above zero. (lowest = 2 or 3 Celcius). Do you think the fish are getting enough oxygen? Dad has been observing just one fish tilted this year. He mentioned he had seen this tilt from other fish during previous Winters and was wondering if it was normal. Should we just watch and wait then? Or would you recommend we use heaters?

  8. Venus January 13, 2018 at 6:55 am

    Hi Emme, I was just thinking about you, and wondering how things were going

    In most cases when a fish tilts to the side, it’s losing consciousness. Winter is a tough time for fish, and even though your fish experienced health issues previously, they had a few months in healthy water before winter set in, which gives them a fighting chance to survive the cold. In their natural habitat, they would experience the same cold water, becoming dormant. Only the strong survive. This is the way it is in the wild, and the not so wild as well. There’s a chance you could lose a fish or two over the winter, but there’s a better chance they’ll all survive

    If the fish has a health issue, the cold water will benefit. Goldfish and Koi alike use less oxygen in cold water, so most health issues are put on hold until the water warms. This is when will see any unresolved issues crop up

    Are any of the pumps still running?

    You have algae, so if any of the fish are hungry, which is doubtful, they can indulge. Lack of food can cause the swim bladder to collapse, which causes the fish to lose the ability to lift or swim, so that’s not the case here

    As long as the bottom of the pond isn’t freezing over, we’re good. I wonder if your Dad is seeing the same fish, or different fish? or more than one at a time?

    Is most of the surface frozen? all or none?

  9. emme January 13, 2018 at 2:41 am

    Hi Venus,

    The koi pond has been dormant for several months now. Outdoor temperatures are always below 10degrees C (range from 3-8). We haven’t fed the koi since the beginning of Winter. I’ve still been checking the water chemistry every few weeks. The fish are generally camping at the bottom of the pond. Recently, my dad has noticed that one of the medium size koi has been lying on its side (gills up) instead of vertically (dorsal fin up). When he went to take a closer look, it swam away. He says he’s seen other koi lie like this during dormancy in the past. Why does this happen? Is the koi too tired? Malnourished/lack oxygen??

  10. Venus November 12, 2017 at 8:21 pm

    If the fish aren’t feeding at all, one pump should be sufficient, but if the weather warms for more than a few days, and the fish show interest in eating, I would plug in another pump. The warmer the water the more action you need. The colder the water the less action needed

    The parameters look great

    I know it’s nerve wracking; dormant fish, but nature is taking her course. Fish that experience dormancy in the winter live more years than fish that don’t

  11. emme November 12, 2017 at 7:12 pm

    Hi Venus,

    The comments box seems to be working well again.

    Tested water today with these readings:
    Ammonia/nitrite~0. Nitrate 5-10. pH=8.2-8.4, KH=110-120, GH=200.

    Outdoor temperatures have been around 10degreesC. We usually just go with the air temperature because we don’t have a pond thermometer.

    The fish seem to be dormant as before as they don’t swim around much and float on either end of the pond. Do you think we should leave 2 pumps unplugged at 10degrees or just 1?

  12. Venus November 7, 2017 at 5:14 am

    Thanks Thuner. All is well

  13. thunder174 November 7, 2017 at 1:55 am

    finaly got in lol at least mine working hope her fishie gets better

  14. Venus November 4, 2017 at 5:45 pm

    Testing comments

  15. Venus November 3, 2017 at 6:31 am

    It’s normal for some fish to reach a state of dormancy faster or slower than others. It’s possible the water is warmer under the waterfall. They’re not too cold though. Your fish can tolerate temperatures above freezing, so your fish are okay. If fish are swimming around, and show interest when you walk up to them, feel free to feed them food high in roughage, but small amounts

    It is a tricky time, but the fish have the answers. If they’re eating, the friendly bugs are eating too. Trouble comes when the friendly bugs aren’t eating, and food is being added to the environment. The food turns to waste as soon as the weather warms, and then the friendly bugs are unable to convert the large amount of waste. If the friendly bugs aren’t dormant, and no food is being fed, they starve and die out, causing a spike as the weather warms. Did that all make sense?

    If a spike happens, you’re ready. You understand the cycle, and are prepared with water treatment

    Ammonia is created from the waste your fish produce, and ammonia is the first toxin to form in the cycle. Some fish keepers look at it as a bad thing, but it’s the food source for friendly bugs, and without it, there would be no life in our natural bodies of water

    You’re not seeing nitrates, the end result of the cycle, because your fish aren’t producing waste. As long as the friendly bugs are dormant, they don’t require food, so I think everything is going well. Time will tell

  16. emme November 3, 2017 at 12:20 am

    Hi Venus,

    It was 3 degrees C out today and the temperature may drop to negative 2 C in a few days. We noticed many of the larger fish seem to be hanging out near the base of the pond under the waterfall. Dormant? Or just kind of floating at the bottom with little movement. We unplugged 2 pumps closer to the waterfall. Some fish are still swimming around.. not sure why. Dad has stopped feeding for almost a month since the outdoor temperatures dropped below 10C. Today ammonia,Nitrite,Nitrate were pretty close to 0 (lowest color on scale). KH was 120 and GH was 220. Hopefully everything will be okay…

  17. Venus November 2, 2017 at 4:39 pm

    No, don’t cover the surface for any reason. If the surface freezes over; all or some, the water will be cold enough that the fish are completely dormant, and won’t need any oxygen. This is the only cover your pond should ever have

    As for the second pump; remember the trouble you’ve had with the water. Moving water is healthy water. I think they would be safe in unplugging the second pump if temps reach just above freezing; say 4.4 ish. Your fish won’t reach full dormancy until then. You may still be feeding at temps of 10 c or 50f. Food makes waste which makes Co2 which reduces oxygen. You’re safe to turn off the pumps if you and the fish aren’t feeding

    If you have any exposed pump cords, best to insulate them; keeps the cords from cracking

  18. emme November 2, 2017 at 3:04 pm

    Hi Venus,

    My parents would like to unplug 2 submerged pumps. They are asking if we should cover the top of that area of the pond with anything to keep it warmer?

  19. Venus November 2, 2017 at 6:59 am

    Hi Emme,

    A very good thought indeed, but I wouldn’t worry too much. With a pond your size, there’s bound to be an area that the pumps aren’t reaching; some quiet spots. The area where the water fall is located for example. To be sure, turn off the pump on the far end. I don’t have a lot of experience with the extreme cold you experience. Here in Missouri we have relatively mild winters by comparison

    I’m sure the water conditions won’t deteriorate if only one pump is turned off. The fish won’t be using much oxygen over the winter anyway

  20. emme November 1, 2017 at 11:41 pm

    Hi Venus,

    Outdoor temperatures are now consistently below 10 degrees Celsius 24/7. The pond guy says that since we have 5 pumps submerged at the bottom of the pond now, the base of the pond may be a lot colder than previous years and may be even too cold for the fish, as the pond bottom would have been warmer for the fish during previous Winters when there were no pumps there. What do you think about his comment, Venus? Do we need heaters? We’ve never had any installed…

  21. emme October 17, 2017 at 12:06 am

    Sounds good. Will keep monitoring the water. Many thanks to you, Venus 😀

  22. Venus October 15, 2017 at 8:07 am

    That is a wow, and a big one at that, considering everything you guys have gone through. This is the way it’s supposed to be with big ponds; easy

    If the fish aren’t feeding, they’re in a dormant state. If the fish are in a dormant state, so are the friendly bugs. As the weather warms, and the fish start feeding again, so will the friendly bugs. No, there shouldn’t be any spikes in the cycle. This only happens when food is added to the pond that the fish don’t eat. The fish will let you know if they’re wanting food by swimming to the surface, so play it by ear

    You did it

  23. emme October 15, 2017 at 2:41 am

    Hi Venus,
    Wow, since the pond leak has been fixed, I’ve just been doing weekly water tests and it looks like the good water parameters have been consistent over the last 2 weeks. I didn’t add anything to the pond last week and when I measured today these were the readings: Ammonia=0.1, nitrite =0.1, nitrate=10, KH=130, GH=240. I might add more epsom to increase GH again but I’m quite pleased by how low maintenance the entire pond has been. I’m thinking it may also have to do with my dad having stopped feeding over the last week (outdoor temperatures are 6-12 degrees C thes days). This makes me wonder though, what happens to the good bugs in the pond when the temperatures are so low? Do they hibernate like the bad bugs? Would water parameters spike once it’s warmer after Winter?

  24. Venus October 5, 2017 at 10:45 am

    The pond pumps produce action at the surface, but the bottom remains calm, which is perfect for Koi, especially if the water is oxygenated on the bottom, and it is. There’s a very good chance the increased action will keep the areas around the pumps from freezing. They say fast moving water doesn’t freeze, but who are they? It depends on how cold and for how long the cold spell lasts. Fingers crossed. I think it will be fine

    It’s fine for your dad to feed toasted wheat germ now, but this mostly depends on the water temps. Large bodies of water take a lot of time to increase or decrease in temperature. As long as the fish are interested, it’s okay. When they’re completely dormant, they won’t come up to feed

  25. emme October 4, 2017 at 9:45 pm

    I see. I’m going to observe that fish a bit longer then. Will let you know if/when I can finally get that limestone, as their hours are identical to my work hours and the commute is very long. Crushed coral maybe I can get in a few weeks.

    The temperature is a lot colder now. It ranges from 8-16 degrees Celsius. Can we stop feeding now? Or still feed once daily? I think Dad just feeds wheatgerm once daily from time to time. Sometimes not at all if too cold in morning.

    The fish do seem much slower in colder temperatures. I’m wondering if the High surface action in the water would be too much for the fish in colder temperatures when they don’t move much??

  26. Venus October 2, 2017 at 9:12 am

    The pink you see in Toby’s fish’s tail fins are caused from nitrite poisoning. The symptoms show long after the fact. Because nitrites rob the blood of oxygen, the blood thickens, and the blood vessels become enlarged, and very visual. The tail fins are the first to show, but if you see tiny patches of veins on the body, this indicates the case was more severe, and the fish may need treatment. The cure is heavily oxygenated water, which you’re providing. It will take several weeks for the symptoms to disappear

    It seems we discussed the idea of crushed coral, which may buffer the water quicker than limestone. Due to the fact your parameters are so low, I might do both. You need gravel on the bottom. This gives waste a place to settle, and helps keep the water clear. Even if you use both, there’s a very good chance you’ll still have to buffer, but, not as often, not as much. Less and less over time

    Some complain that the crushed coral clouds the water, so rinse it off, and leave it in the bag. Place the bag close to the fountain; close to moving water

  27. emme October 2, 2017 at 2:18 am

    Actually, instead of limestone substrate for calcium, can I use crushed coral? I found a decent aquarium supply shop downtown and it’s easier to get to for calcium if coral is a viable source! Not sure how much to use/buy though…

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