400 gallon project

[MitchM]

A few unknowns:
Is the bacteria was coming from inside the fish? The medication won't be very effective if the bacteria originated from outside.
What will the liver do to the erythromycin as it passes through?
I have no idea what the dosage would be for taking it internally.
HAving said that, it could be worth a try.
What size tablets do you have? Maybe we could figure out a concentration from the recommended tank treatment.