I agree with fnesr 100%,thats why I said "most" major injuries. Some just never fully heal up or heal up so slowly it's hard to see the improvement. I'm sure some species heal faster than others,I have never had a gudeon myself...has it ever been injured before? One thing I noticed; my pacu heal up from scrapes/missing scales faster than my Oscar. Maybe thats a general indicator of their healing abilities...just a thought.