Koi on side barely moving

[Sarah Laupp]

I noticed one of my koi was laying on its side at the bottom of our pond. I checked on it over the course of 20 minutes and it didn’t move so I assumed it was dead. When I went outside to get it out of the pond it started swimming, but it went back to the bottom and laid on its side again. It’s mouth is open, unnaturally. Also, it looks like it’s may have a bulge on its side, but I’m not sure as I don’t usually see it from this angle. It’s otherwise been healthy as far as I know. We have 9 other koi in the pond acting normal. Any thoughts on what might be happening and how I can help it?

 

[WaterGardener]

Have you tested the water? How many gallons in the pond?

Pretty fish by the way. I'm a sucker for the yellow ones.

 

[Sarah Laupp]

Thanks! I did test the water. Alkaline levels are a little low but not much. Everything else looks great. Pond is ~2500 gallons. We have 7 large koi and 4 babies. Filters are cleaned regularly and the waterfall is flowing well. None of them are moving around a whole lot since it’s been getting colder, but I’ve never seen one on its side like that before and with it’s mouth open… something is off I just don’t know how to fix it!

 

[DerekOR]

I think they do that when they are very stressed and having difficult breathing. Are there any signs of worms attached to it especially around the gills? You may have to look very closely to spot them.