I'm not sure if the use of Baytril being so widespread is causing some resistance to it's use, but I now commonly use the 2% dose recommended using the 5% Baytril for the 1st injection, then follow up with 1 1/2 dose for the remaining. I don't even mess with the recommended dose anymore. I've done this over the last year with many many fish after I've seen no improvement of the ulcer and have never had an adverse side effects even in fish at the 5-6 inch size. I've seen injection site irritation on occasion, but I've had that happen when using the recommended dose (1/2 recommended dose for 5% solution). The lower dose simply isn't effective anymore in my experience.
UMKC 2013 Koi Show & Product Expo
August 10th & 11th, 2013