It might be ick, an infection of the parasite Ichtyopthirius. 1 } w9 M7 E( @ 0 c1 A0 ?2 d* E" \$ t1 a gYou 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.* y: N' o: }6 F8 f8 |
. l8 l0 _% [6 a( G$ X* _( H- XIt might be hard to keep all the infected fishes, but treatment is necessary to protect uninfected ones.# B. o; ^0 R e5 i) P- ?
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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?5 ~4 K* `: r5 k
2 ]& y. u1 R: [8 M6 _, n$ bNo, they are cold water fishes, they can survive our winter outdoor as long as water is not frozen and exchange of gases can continue.