@TheRealDmorty217 I've tried CP on 3 different Hippos now (at different times) and they all died. Same MO: They refuse to eat, hide and then die after about a week. Same thing that has happened with all Sixline and Melanurus wrasses I've tried CP on (but flasher/fairy do fine.) I can't explain it, as all other tangs I've used CP on seem do well in it. Of course, Hippos are their own unique genus of tang so that's how I rationalize it. Similarly, I suspect (but cannot confirm) that all Halichoeres & Pseudocheilinus genus of wrasses would not do well in CP.
If I were in your shoes and TTM is not an option, I would treat the Hippo with Coppersafe. They are generally pretty hardy, and I've not had any issues running Hippos through copper in the past.
I can do TTM but wanted to avoid more work for myself if possible. (If I get the yellow belly... Sounds like TTM is the only way to go) I have a 5 year old Melanarus that I have put thru CP now 4 different times without any negative effects (not sure if that's a fluke or not). I have coppersafe but I have never used copper before on fish... I have used cupramine but all I accomplished with that was giving the angel that was being treated Lymph that took 3 months to go away. Thank you for the info, still haven't decided if I'm going to get the yellow belly or not