I'd agree there is no guarantee it will work, however it is one of the more reliable treamtments and if done properly, has a much higher success rate than many. There are variables; some strains of c. irritans are resistant to hyposalinity. The actual specific gravity suggested is 1.009, and fish have been kept at slightly lower sg with no ill effects. You need to have an accurate measuring device and need to be diligent about monitoring salinity and pH. My personal experience with hypo has been largely positive. Copper is an alternative therapy, but some fish don't seem to tolerate it as well. Some would argue that hypo is not tolerated by certain fish but IME, all teleost reef fish can handle the procedure.