I have/had a Large, dinner Plate sized Monti Cap and noticed some STS recently. Params are awesome, and it's the only one of my Corals doing it. It's in fairly high light, and Good flow. I noticed my Orange Monti cap was quickly receding from the center area This was it prior After Surgery- Good 'ol Dremel Tool! I of course went Around the tumor, leaving only healthy tissue Not sure I'll ever know what was causing this, and really don't care- as long as it's gone.