Hi,
I'm out the country (UK) and have been for the past month and will be for the foreseeable future. At the moment our Koi (which are 3 x 6-9" and 10 x 2-4") are in a temporary set-up whilst we complete our pond. They are in an Intex Pool and have been since October with a pump/filter running since then. The filter is way oversized for the pool and we are also feeding relatively lightly in the temp set-up. We had an air-pump running through winter which froze and I figured I didn't need to get it replaced because the pool is only about 800 gallons and the filter is returning from two outlets about 20-30 inches above the water level so the return is making quite a splash and the water is being turned over probably twice an hour, if not more.
Everything has been fine since they've been in temp set-up since October. No issues, illness or death. My parents who have been keeping the pool ticking over and feeding the fish (they are under strict instructions not to overfeed) informed me they found a small Koi dead behind the filter pipe and it looks to me like it's been there for at least a few days I'd guess due to the condition of it. All other Koi seem healthy and I had them do a small water change when they informed me of the dead Koi. I got a picture.
Can anyone see any signs of anything specific or a possible cause from the picture? (edit: I also can't even tell what variety of Koi it is...possibly looks like a Kohaku but it's hard to tell)
Thanks