Hi, I have several Koi carp had them for over 15 years now, I have had no problems with their health winter or summer, they are now quite large fish over 30 cms = 12 inches long , however for the past 6 months one of the fish makes a point of sticking it's tail out of the water, the tail appears to be unmarked and is free from any spots or injuries, apart from this this fish acts normally eating well etc. Any suggestions why this is happening? My pond which is above ground, the water has tested normal Ph, amonia,etc.
Brian.
Brian.
