It might be ick, an infection of the parasite Ichtyopthirius. + Z' C6 O3 s9 ]! \8 q2 a! e - A' i/ {' K4 }2 jYou can increase the water temp up to ~28C and give them drugs (basically Cu2+ ions), plus large quantity of water change. Google for further details.. x. p5 S: p9 ]4 B ?( `
2 }7 w; \2 o7 |2 q$ PIt might be hard to keep all the infected fishes, but treatment is necessary to protect uninfected ones.+ P* {1 g8 z R2 ]
" s' C& ^8 w8 s; |' m8 X/ `By the way, is it necessary to have >20C for koi and goldfish?
Quoted: By the way, is it necessary to have >20C for koi and goldfish?, t$ }* i5 @' g9 l% Q
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No, they are cold water fishes, they can survive our winter outdoor as long as water is not frozen and exchange of gases can continue.