this tank needed dental surgery at the encroachment phase, when it was on first rock but how easy is hindsight agreed
even still, you'd be surprised what it may still do. this is the biology of your invasion based on about ten thousand searchable invaded tanks restored:
nutrients never caused your issue, and only the luckiest of stasis changes would ever set that back. no reefer could command that to die by nutrient changes without killing/bleaching coral in the process across 3 tanks in a row, whatever might have worked on one after ten trials wont xfer to the rest. this is not a nutrient issue, x that out from the forumula imo.
this was simple nonquarantine + allowed growth but I don't mean that bad. you weren't wanting it there, but the animals added chose not to act and they were a decent move to try agreed. there was still an intercept point which was low work in the beginning, and high work now, but thankfully *measurable* before you take on work, unlike any other approach.
most of us will import various invaders over time, I don't qt at all, but pico reefers use a different approach when the encroachment phase begins, literally the 1st spot seen the size of a thimble the 1st day its seen:
the rock is lifted out and a steak knife is used to score out the anchors, and the invader, regardless of id, in a rasping motion like we'd hoped urchins w do, and do well in some tanks. Peroxide is then applied to the
cleaned spots not the invaded ones, because our surgical digging action already made the invader gone
*nature uses raspers on your invader, which is why it works in some tanks*
the steak knife is man rasping, deliberate, on target, awaiting no other actions other than to will a clean rock immediately.
a steel knife tip and surface abrasion... like a dentist rasps plaques and leaves a little insult bleeding on the gums, is how you measure and take back ground anything indirect simply allows more growth.
pre modeling
before doing your whole tank, only for it to possibly grow back, mini model something
take an easy to work portion, run the test, watch it in 5 days compared to the control areas and see which looks better. pls take pics if you do this, ill link it to massive tank cure threads and your job is big if you want to force it clean right now.
If that was my system, I wouldn't even consider using anything less than 35% peroxide the 3% wouldn't be worth my time. 35% takes special prep, its mighty dangerous.
Id prefer your invasion to the worst of dino invasions btw, at least yours does respond to rasping since its an anchored invader. anchors only run so deep, if it grows back, you didn't rasp deep enough. that means it would have taken a parrotfish, something that bites chunks off the reef, to cure it in nature if this occurs.
my method isn't crazy or weird it only sounds that way. fact: no other method can beat that one above for this specific invasion, history, per pics and this thread.
b
I would love to take on this invasion btw if you ever want to. after we mini model a few rocks and they behave, then we upscale.
rasping is how you work around the sps border areas and avoid the non targets.
you must take out the rocks and do this externally to do it right; we're not trying to re fragment inside the very DT we want to fix.
Im not denying there isn't 13 other ways to fix that. Im stating they're not as thorough, fast, past due, or measurable before action

They're all less work though, and that's why only the 1% does rasping. They do it on all subsequent tanks lost after invasion #1, we were driven this way we were never taught this way in the reef books that gave all instruction. Those books got us invaded~ due to lack of presented options.
this crazy way above is literally the only way guaranteed to preserve your coral, all other methods subject your corals to the very changes in stasis you hope to eliminate a very rooted, nutrient and light-independent invader. you needed a grazer for this job, there's nine+ in kitchen drawer as we speak.
your invader means literally nothing bad about your tank, that may look bad to us, but its steak dinner to a parrotfish or a hawksbill turtle, it
belongs on a reef anywhere the frags ride into.