I've been following the cipro thing for a little while and just would like to say "hats off" to the innovator of this treatment method who I think is Minh.
Have you tried other dosing schemes? I have read that enrofloxacin, for which cipro is a metabolite, in bath formulation, will reach a steady state plasma concentration in fish before 5 hours by crossing the gill membranes. Also, at therapeutic levels, it takes 30 minutes to effectively kill bacteria. I could not find the pharmacokinetics in fish for cipro but imagine it is similar.
Night time baths, or even daily 6 hour baths could be effective to prevent loss of color.
Also, injection into the tissue may be another route to prevent removal from the display tank.
Just thinking......