opened gills on Koi fish

Question
Aloha Chris
I've got 8 kois in a pond.  Recently I noticed two of the kois have their gills opened and stay open; normally the gills would be open-close, open-close motion.  It worried me becuase I wonder if it somekind of fish disease and can the rest of the kois become affected by it.  What with the gills stay open?
Thanks,
James

Answer
Aloha James!

It sounds like they are having difficulty breathing. Lack of oxygen in the water can be one cause. There are tests available to measure the oxygen saturation of your tank water.

Check the other water chemistry also. Elevated toxins like ammonia and nitrites can cause fish to have difficulty breathing. Toxins can rise from many different possible causes; the biological balance was disturbed, the tank is new, the filter was changed, gill disease, etc... Check the color of the actual gills themselves. Are they bright red, cherry red, reddish-brown, pink?

Until you get your test results, the first thing to try is a water change and more aeration. Remove 25% of the water and replace it with fresh. This way, if there are toxins present they will be diluted. The extra air will help them absorb more oxygen too.

Let me know what the test results are if you aren't sure what to do from there.

Followups welcome

At Your Service;
Chris Robbins