Just to share my experience, I've lost all of the following to Hem. Septicemica: 2x 10-12" Endli's, 1x 10" Lap, 1x 10" P. B. Koliba, and 1x 4" Endli.
Total I've saved: 1x 9" P. Endli "Tikinso Guinea" + 2x 10-12" P. sp. Hybrid Guinea.
And to be honest, the ones that I saved are the ones who've been infected the most severely, and I was blown away that they made a recovery. I've basically used every form of Metronidazole and Erythromycin that we sell at the shop, and never had luck in the past, though SeaChem Metro + Kanaplex have done absolute wonders for me with other types of fish. The last treatment I used, and the only one I was successful with was Aquarium Solutions "Metro Plus" which is a slightly less concentrated mix of Metronidazole, but is also supposed to help with slime coat regeneration, which my fish needed pretty badly at the time, and I will never use Stress Coat again, and refuse to sell... Anyhow, the only thing that worked for me was daily usage of: full 75gal dosage of Metro Plus, 40gal treatment of epsom salt, and 35-40 gallon water change, all for 5 days.
I hope your fish pulls through, it would be terrible to lose a fish you've had for so long.
Total I've saved: 1x 9" P. Endli "Tikinso Guinea" + 2x 10-12" P. sp. Hybrid Guinea.
And to be honest, the ones that I saved are the ones who've been infected the most severely, and I was blown away that they made a recovery. I've basically used every form of Metronidazole and Erythromycin that we sell at the shop, and never had luck in the past, though SeaChem Metro + Kanaplex have done absolute wonders for me with other types of fish. The last treatment I used, and the only one I was successful with was Aquarium Solutions "Metro Plus" which is a slightly less concentrated mix of Metronidazole, but is also supposed to help with slime coat regeneration, which my fish needed pretty badly at the time, and I will never use Stress Coat again, and refuse to sell... Anyhow, the only thing that worked for me was daily usage of: full 75gal dosage of Metro Plus, 40gal treatment of epsom salt, and 35-40 gallon water change, all for 5 days.
I hope your fish pulls through, it would be terrible to lose a fish you've had for so long.