Update -- fishy's fins look the same today. They had been getting worse each day for the past 4 days so I was happy to wake up and see he hasn't deteriorated further. i'm on day 2 of the erythromycin treatment. The medication is meant to be used in a tank and there were no instructions provided for use in a small QT tank where water changes are necessary. For example, on day 2 the instructions tell you to add another dose. Since fishy's ammonia was high (0.25-0.5) I did a 75% water change. I added the new dose, but it wasn't clear if I should 'replace' the dose that I removed with the water change. In other words, should the medication be getting stronger each day, or does it breakdown and you're simply 'toppin it up' so to speak. I added the regular dose, but I'm not sure if I should have added more.