Koi Keep Dying!

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Hi,

I have had a pond for two summer seasons, with small koi (4”) that I have introduced on occasion. Originally I had 3, and have replaced 2. Both replacements did not survive, and I have one remaining that looks like it is on its last legs. It has a sore (looks like an open sore with flaking skin) on the side of its head, and all of the previous dead fish had a similar looking wound. This one has grown since last summer but it does not seem interested in feeding and is very reluctant to come to the surface. Lately is seems immobile on the bottom unless I startle it.

I have noticed an odd looking bacteria (or pond waste?) pattern forming on the walls of the pond and the rocks inside the pond, but have no clue how to identify if it is normal or a parasite or other harmful agent.

For reference, the pond is approx. 900 litres, and I have several pond plants in the water. The one time I had the water tested it was normal (no elevated levels of any noticeable toxins)...

Does anybody know what is going on?? Any recommendations on how to remedy the situation?? I’ve attached pictures.
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addy1

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How big is your pond? What are your water tests like? What kind of filtration do your have?

Welcome to our group of pond lovers!
 

j.w

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@SpencerJ
Does not look good. I am no expert on disease but I would not get anymore fish till this is figured out. Hope someone on here can help you w/what exactly it is. Looks kinda like it's scales stick out some from the body and some kind of infection or wound on the gills/head.
 
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Looks like dropsy (swollen body, raised scales) Sorry to say but in my experience with dropsy the fish will not survive.

900 litres is about 237 gallons which is too small for koi long term.

I would recommend getting a water test kit and check your water parameters before adding any new fish.
 
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I agree about the dropsy :( Not sure about the head, it could be Heximita, otherwise know as "hole in the head disease", or some kind of other secondary infection. Sadly, it's doubtful the fish will survive.
 
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How big is your pond? What are your water tests like? What kind of filtration do your have?

Welcome to our group of pond lovers!
The pond is a concrete manhole section 4’ (1.2m) diameter, 3’ (.915m) depth, and was placed inside a rubber pond liner. There is a bed of sand and gravel at the bottom, and I have 3 different pond plants (I assumed those would help naturally filter water?!) The water level is probably around 30” (.762m) so I calculate the volume of water at approx. 900 litres. The filtration system is a Laguna PowerClear 1000 All-in-one. It has a UV lamp and filter with a permeable stone layer.

I’m not sure what the water test results were precisely. I had taken a water sample to the fish/pond store when I first encountered the issue with the koi dying off. They do the testing for free (they have several pond experts) and they said the water was not the issue and that they didn’t see any indication of nitrites (nitrates) or other indicators that they were concerned about.

Is dropsy caused by a parasite or bacteria? Does the pattern of “stuff” on the rocks in the image look familiar to anyone or suggest they it’s a bacterial issue?


Thanks!
 
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Looks like dropsy (swollen body, raised scales) Sorry to say but in my experience with dropsy the fish will not survive.

900 litres is about 237 gallons which is too small for koi long term.

I would recommend getting a water test kit and check your water parameters before adding any new fish.

The general rule of thumb I had read was about 1 inch of fish per 10 gallons, so I would’ve expected about 24 inches of fish would be sustainable. For context, my parents have an identical pond setup with at least 6 decent sized koi in it. Their pond water is far less clear than mine, but I don’t think they’ve ever lost a fish to disease and have had them for over probably 15-20 years.


If the pond is too small for koi, what other fish/aquatic life would be suitable? Frogs? Turtles?

I live in Calgary, so i have to winterize the pond, but this koi lived all through the winter in there and now he’s giving up on me!!
 
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The general rule of thumb I had read was about 1 inch of fish per 10 gallons,
Welcome @SpencerJ - sorry that it's fish trouble that brings you here, but let's hope we can get you sorted out and you'll stick around.

That "rule of thumb" you quoted gets mentioned a lot here. Unfortunately it's misleading. The issue with that math is that one ten inch koi has a greater biomass than ten one inch koi. The amount of waste created is exponentially larger. Someone shared a link the other day - I'll see if I can find it and post it again. But in general, 300 gallons would support a few goldfish nicely. Any more than that is a recipe for disaster.

I'd be shocked if your parents have 6 koi living in under 300 gallons of water for any length of time. How big are the fish? After 15 years, they could be as much as 2 or 2.5 feet long. And clear water isn't really the issue - pond water doesn't have to be clear to be healthy and the clearest pond in the world can be unable to support fish if the parameters aren't right.

I'm wondering about your cement "manhole". (I'm imagining a piece of culvert - is that what you mean by manhole? A photo may help.) Could the cement be leaching into the water and keeping the pH too high? Have you tested the pH? Although it appears this fish his suffering from some kind of bacterial infection. Is the inside of the pond smooth?

Your sand and gravel base may also be causing an issue - how deep is the substrate? Waste could be building up on the bottom allowing bad bacteria to grow.

And yes, pond plants will help filter the water, but they do much more for a pond if they are planted directly in the pond. Keeping them in pots is far less effective.
 
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So sorry to hear about the problems. It looks very distressing in the photos. I suspect it is gill flukes or skin flukes and has nothing to do with your water on this occasion. Flukes can be up to about 3mm long and cause that sort of damage. Are the fish rubbing against objects in the pond? I agree with what Lisa has said about size of pond but on this occasion I suspect it is parasites. Go to your fish store with the photos you have shown here and if they agree then prazi will fix the problem BUT the damage is already extensive and will take a long time to heal. Also dont add anything else until the parasites are eliminated from the pond completely.
Ray
 
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The general rule of thumb I had read was about 1 inch of fish per 10 gallons, so I would’ve expected about 24 inches of fish would be sustainable. For context, my parents have an identical pond setup with at least 6 decent sized koi in it. Their pond water is far less clear than mine, but I don’t think they’ve ever lost a fish to disease and have had them for over probably 15-20 years.


If the pond is too small for koi, what other fish/aquatic life would be suitable? Frogs? Turtles?

I live in Calgary, so i have to winterize the pond, but this koi lived all through the winter in there and now he’s giving up on me!!
So Spencer how did it turn out? Did you get prazi for the flukes?
 
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