A Koi keeper has 3 main problems apart from KHV:
3 White Spot. and this one is linked to the previous two.
White Spot is a stress related infection - no stress no white spot. You don't have to be a brain surgeon to under stand that one.
When fish have been infected to a high degree no treatment works - they just die.
White Spot is ichthyophtririus or ich as its sometimes known. It is a ciliated protozoan that encysts under the skin of the fish. These encysts gives the disease its name as they look like small white pin heads.
In Koi infection it mostly, but not always, takes place in the gills, and it's the gill mode that is the killer. White Spot on the gills cannot be seen unless it is tested for and so the wrong treatment is often used and the fish does not die with speed.
There is also a problem with this disease known as asymptomatic carriers, which can remain in a pond for an indefinite period until a new fish is added which are immunologically naive to White Spot will contract the disease immediately.
If a fish is introduced to pond containing an endemic ready infected but asymptomatic group of fish and it survives without treatment then it will have the same immunity as the other stock. However, if the new fish cannot resist infection then will show signs of the disease very soon and give the impression you have introduced an infected fish but in fact it's your stock that are at fault.
Damage to the gills is the main way it kills, but also damage to the skin with secondary infections. In fact, unless you have an epidemic, its mainly the secondary infection which kills a fish even though it may have been cured of White Spot..
Immunity will not show its self in quarantined fish. Fish look very ill with White Spot like us having the flu rather than a cold. Most White Spot infections are brought into a pond by new fish either netted poorly or transported in poor conditions.
An outbreak in a pond with no new fish added indicates the system is at fault and needs sorting immediately, before any treatment starts.
When buying fish, if there is one that looks like its was one number of the lottery win, then there's a good change it has white spot.
Do not believe the magazines and books -White Spot can infect in Spring, Summer, Autumn and Winter. I know I've seen infections in mid winter. All the cold water does is slow down the time from encysts cysts to spores and re-infection.
I've already stated I don't give out treatments on this site, but nothing works other than malacite and formalin. I know it will harm your filters, so run a by-pass. You are between the proverbial rock and a hard place. If you don't your fish will die. Use fresh mix not rubbish that's been mixed in bottles when the Titanic went down.
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