Thank you all so much for your input and advice! Still Learning - you are correct, my display tank is full of inverts, live sand, and live rock. We decided to QT the fish and treat them separately in the 29 gallon; the fish will be out of the display tank for 8 weeks (in accordance with the information provided in the myths and facts thread) and so this should allow the display tank enough time to rid of the parasites while the fish are in QT undergoing treatment. Hopefully upon reintroduction we will no longer see this problem. Cowfish are ok with copper treatment and apparently handle it quite well (according to some of the sources I have found) - she is my favorite fish though and it would really upset me if I lost her. I am particularly protective of her and will continue to look into this. Kevin, gosh it is discouraging to hear about what happened to your tank! I pray that we are not in this same situation...we have also had our run-ins with velvet and this method apparently will help with velvet, too. I can only hope that we do not encounter what you went through. Thanks for the advice about stress and keeping them well fed. Our fish appear to be happy other than the tell-tale spots that they have. They all have good appetite, too, which is usually my indicator of how they are feeling.
Thanks again so much for taking the time to respond and provide your suggestions!
Julie