Any idea what this is?

[richyd]

I'm getting a bit worried about this now. almost all the white parts of the fish have turned black. Its like its morphed into another fish.
Other than that its behaviour has not changed whatsoever. I've checked my water again and its precisely the same as last time, nothing to report.

 

[richyd]

I'll get some pics tomorrow when I clean my filters out

 

[Shdwdrgn]

I didn't see it mentioned here, but what size is this fish, and how long have you had it? I have bought several young koi that had bright colors, only to have their backside turn almost totally black during their first Summer in the sunlight (even the ones I kept indoors all Winter without any sign of color change -- they get out in the sun, and start turning black).

You also mentioned a comet that is turning colors, but I am confused by what you said above. Is it a black comet that is turning red (completely normal and typical within the first 2 years of age), or is it a red comet that is turning black (which I've never heard of)? If the comet is turning black, then definitely wait for an answer from one of the others, but if you have a younger black comet turning red, then this is not related to your koi's issues.

 

[richyd]

I didn't see it mentioned here, but what size is this fish, and how long have you had it? I have bought several young koi that had bright colors, only to have their backside turn almost totally black during their first Summer in the sunlight (even the ones I kept indoors all Winter without any sign of color change -- they get out in the sun, and start turning black).

You also mentioned a comet that is turning colors, but I am confused by what you said above. Is it a black comet that is turning red (completely normal and typical within the first 2 years of age), or is it a red comet that is turning black (which I've never heard of)? If the comet is turning black, then definitely wait for an answer from one of the others, but if you have a younger black comet turning red, then this is not related to your koi's issues.

This commet (not koi) would be just over two years old (approx 4-5"). He was the sole survivor of my parents previous pond disaster. After the disaster I ripped out the liner, everything, installed a new liner, new plants, new filtration and put him in. He literally was unseen for months, until I added some ghost koi, orfe, shubs, commets, goldfish - then he reappeared. Maybe he was lonely??
The pond is now just over a year old and i've been quite successful.

To clear up the other point, my younger commet (black) started developing redness. And is now very nicely coloured.
However the big one in the pic, the white parts are almost completely black.

 

[richyd]

Hope that makes sense lol . sorry