Never seen septicemia so bad as that, i would issolate the fish, also how many gallons is the tank, plus how many fish and which type.
Corys are very prone to bacterial infections, to be honest he needs a good antibiotic, but they are not available in the uk.
Only med is anti internal bacteria med by interpet, but it might be to late as septicemia is blood poisoning.
Not the writer of this information below.
Septicemia
Symptoms:
Fish may have reddening at fin bases, blood streaks throughout the fins and body, small hemorrhages around the eyes. Dull listless behavior and lack of appetite may also be present.
Cause:
Systemic bacterial infection caused by various bacteria, including Aeromonas, Pseudomonas and Vibrio. The illness is often brought on by poor water quality or as a result of parasitic infestations or other infections. These bacteria enter the blood stream and circulate through the tissues causing inflammation and damage. Inflamed blood vessels in the skin and at fin bases stand out. Blood vessel and heart tissue damage cause hemorrhaging and consequently leakage of body fluids into the abdomen, which may lead to Dropsy.
Treatment:
Water conditions must be improved for all fish in the tank, regardless of how many fish are infected. Check your water’s Treat with Kanacyn or Tetracycline as well as with a medicated food if the fish will eat. If parasites are suspected, all the fish in the tank should be treated with antiparasitic medication. Using salt to help restore osmotic balance might be helpful.
