Strange markings on oranda tail

[HairyFeline]

My oranda (4 years old) was orange and white when a few months old and gradually lost the orange as she got older. Just the last couple of weeks I’ve noticed these stripes in her tail; not typical of disease from what I can tell as they’re not running the length of the tail. Only new thing in the tank is Stanley, a nerite snail, resident for three months. Tank is 94 litres, water tests are perfect, shares with one other oranda who seems just fine. Water temp is 21 degrees. Any ideas?

Pics pending!

The tank’s maybe a bit on the small side, what are the parameters like?

I’ll have to do another test for exact values, but pH, NO2 and NH3 all spot-on perfect. Have tested three times, once at local fish specialist in case my test kit is dud (water sample tests not dipsticks). All the same…all say ok.

Interesting to think on tank size; I thought the 94 would still be ok for these two…they’re not big, maybe three inches nose to butt.

Thanks for your reply!