You should lift it out and do surgery on it then I’ll link it to a giant thread on reef tank surgery
Like a bad tooth
Doc works on the tooth, not just surrounding mouth, doc literally targets the tooth -while- managing the other healthy parts of our mouth with dedicated cleaning during a dental visit. That mode of thinking can save your whole tank from being lost, because it’s an attitude not a wait for ID or some tank measure to allow a hesitated attempt.
When you lift it out and do surgery and put it back cleared of very risky red brush algae that I have twenty threads of it wrecking tanks, you change the course of your next invader by foregoing identification for direct decisive action. This particular one is easy to beat, next one might not if allowed to mass.
Hesitation is the real risk. Not an organism
Surgery=
That coral can stay in air for 30 minutes and not die, so be deliberate while working. It’s a 5 minute job, he’ll be ok.
take it out and use a knife to debride it all off the skeleton being directed, scraping, scratching and rinse in saltwater
Work it clear via knife and sw rinse = what happens exactly to plaque during dentist visit
When it is clear due to your immediate disallowance then apply peroxide to the cleaned portions outside the tank as you work the frag. Let it sit, rinse off, put back a clean tooth
Regarding the rest of the tank supporting that growth, you may need additional work but for the matter of that tooth, can be fixed in 15 minutes. Take pics!
If you try and work the frag in tank, or kill it off and let it die internally, you get fragmented target spread all over. It’s a tank wrecker. Params don’t cause this, it hitchhikes in strictly, and it’s genus or species doesn’t factor in action. The second you sensed action needed it was accurate.