Dead Koi Fish... Why Are They Dying?

HI Guys,

Important: I put this in the goldfish section because my goldfish may be at risk as they are in the same pond as my dead koi.

So I told you all I had a koi fish that was suffering from severe mouth rot and I was advised by a senior member to give it a salt dip with Melaflix. That's what I did about 4-5 days ago and it died today.

I've bought 3 koi from my LFS and 2/3 of those koi have died. My water parameters are perfect: pH is 7.5, nitrates and nitrites are 0, but the tank is small (100 gallons. I know it is overstocked and I am currently in the process of building a pond.). This shouldn't have made a huge difference though because they are only a few inches and the size of feeder goldfish as of now. I also have some feeder goldfish in there and they are going super strong, putting on about a quarter inch a month.

When I found my koi this morning hiding in the plants, barely moving, I knew he had given up. Upon closer inspection, I found that his upper jaw bone was revealed and there were multiple holes in the bone. The actual bone had split into two pieces so a piece of his upper jaw bone was just sticking out of his mouth. My other fish were picking on him and he was so weak that I had to euthanize him.

My concern is: The 1st koi that died had almost the SAME EXACT PROBLEM. It was like deja vu. First his mouth started to rot and I didn't notice until there was a big growth on the lip. By then some of the lip started to rot and by the end of two weeks (exact same timeframe as my most recent koi death). Then his upper jaw bone broke and a piece of his bone was just sticking out his mouth. I didn't euthanize him, although I should have and he ended up dying.

What is happening? If it is some sort of parasite, why hasn't it spread to my feeder goldfish or other koi fish?

Little bit of background on my LFS: They only started stocking Koi and goldfish about a year and a half ago. Their prices are the most competitive I have ever seen at about $8 per baby koi fish. This store usually isn't the most competitively priced, but carries the highest quality tropical and saltwater fish I have ever seen in my life which is why I give them my business. While I didn't find any dead koi fish in the tub I got my koi from, I did see them pulling out a dead koi from one of the other tubs. I asked them about it and they said it was a new shipment and not all of them make it... don't really know what to think about it.

 

Here's how I would treat mouth rot: Great water quality, everything always 0 maybe nitrate up to 5, hydrogen peroxide swab, if you really want to go advanced antibiotic injections.
It could be the Koi you are getting. Make sure when you buy them they aren't rubbing, and their mouth isn't red.
Is the fish eating? If it is, it's not mouth rot. Pictures would really really help.

 

Here's how I would treat mouth rot: Great water quality, everything always 0 maybe nitrate up to 5, hydrogen peroxide swab, if you really want to go advanced antibiotic injections.
It could be the Koi you are getting. Make sure when you buy them they aren't rubbing, and their mouth isn't red.
Is the fish eating? If it is, it's not mouth rot. Pictures would really really help.

The weird part through it all was that my fish were still eating and acting normal. It was only in their last moments did they lose all their strength. I made a post about my situation earlier.

Here is the link:

This link includes the story, pictures, exact water parameters, and other important information. I would love for you to take a look at it. Thanks.

 

Now that I saw the picture, It's definitely not mouth rot. I am not exactly sure what it is, I will post the pictures on a different forum that I go to which has a vet. WIll relpy as soon as they do. For now, add aquarium salt, and up your water changes to 50% twice a week.

 

Now that I saw the picture, It's definitely not mouth rot. I am not exactly sure what it is, I will post the pictures on a different forum that I go to which has a vet. WIll relpy as soon as they do. For now, add aquarium salt, and up your water changes to 50% twice a week.

Thank you so much! I will be sure to add salt

 

So the answers I got were more water changes, feed them more, why do you feed so little? I think baytril injections would benefit greatly, along with a hydrogen perxide swab. Good luck!

 

So the answers I got were more water changes, feed them more, why do you feed so little? I think baytril injections would benefit greatly, along with a hydrogen perxide swab. Good luck!

I was only feeding them little bits because they say not to feed with mouth rot and I had a massive algae bloom. They reccomend feeding less to suppress the algae growth. Do you know what disease it is? Is it contagious?

 

I was only feeding them little bits because they say not to feed with mouth rot and I had a massive algae bloom. They reccomend feeding less to suppress the algae growth. Do you know what disease it is? Is it contagious?

Does it look like columnaris? do a quick search on google. If so, I would recommend baths in potassium permagrate and medicated food with kanamycin. Best of luck.

 

IMO mouth rot. Since it's caused by bacteria or parasites, most likely contagious. But you will need to treat the entire tank with more water changes and salt, also melafix and pimafix to prevent other diseases while the fish are weak, might also add Stress Coat. Now that I think about it all of the above except melafix. Do a hydrogen perxide swab where the infection/problem is on, and after a few days do a baytil injection if there is no progress. Do this to any fish that you see not eating, red mouth, rubbing the mouth, etc.