This is a massive abscess. As you can see, the fish has a
swollen head and reddening of the fins. This is a good indication that sepsis
has started. An abscess must be caught early as large ones, as shown on this
picture, nearly always lead to sepsis i.e. blood poisoning.
Sepsis mostly only affects one fish in a
collection at any one time. This condition is when bacteria - mostly gram
negative - gain entry to the fishes body via wounds or through the gut wall.
The bacteria can cause the failure of the internal organs.
Most
symptoms show themselves as clamped fins, popeye, reddening of the belly or
eroding fins.
In this type of cases the bacteria is inside the fish
body and are unaffected by water born antibiotics such as ulcer cure (a load of
rubbish!). Injection is the only form of treatment and is far better than
adding antibiotics to food to the pond water. The latter in my opinion never
works.
A fish with sepsis can look
like its jumped out of the pond then jumped back in, and will be in a very poor
state. If the disease is not caught in its early stages it will not respond to
any treatment
Classic
case. One of the best photo of this disease I've
seen