We always take tanks apart and clean things externally like the rocks and the sand, de construct-clean because it lets us remove waste and plugging detritus and we can kill the invader vs coax them out slowly
By rule of being basically an apartment complex to bugs and myriad life, when live rock is plugged by blanketing mass regardless of ID, this withholds the detritus the live rock should be emitting into the tank for removal and this fuels more blanketing as a cycle
It's true large tanks cannot rip clean as easy, to force targets out, so the various dosers and additives are usually a weeks long event trial and error
If your tank was mine and it was too huge to take apart, then what I'd do is spend a weekend hand siphoning out 100% of the mass, every bit of it off the rocks and sand, then I'd install a uv sterilizer rated for a pond of about five thousand gallons. I'd continue hand guiding regrowth as the uv helps, and then in time the uv can be removed and the growth regardless of ID will stop if the guiding supporting removal work along the way was sufficient.
If your updated pics show more trouble on the sandbed than above, that bed may need to be removed for a while until the rock is reclaimed, the physical work mode is all I'll use but it's not popular for large tanks they always want no work fixes/ something from a bottle
It's airways tricky because we'll hold onto single animals above what the greater system demands... for example if wrasses are preventing removal of sandbed from a system where sb removal is indicated, then wrasses outweigh the importance of saving the system but these extremes need only be considered after a few attempts using the commoner means are tied. Re home for a while any animal that prevents us saving the tank... Add back only after no regrowth using zero controls
If you keep getting rebound growth even after really decisive moves, then eventually you'll have to make the tough choice of part cleaning the tank with sandbed detritus cleaning or just waiting longer for normal methods to hopefully work... rip cleaning doesn't have to come first the easier means can be tried to see if they'll work
Outside of direct kill and cleaning, the ultimate fix and the reason no pico reefs online have any sort of recurring invasion issues regardless of ID, the most popular move for large tankers is adjusting nutrients and adding competitive strains of organisms/various retail purchases
** One thing the peroxide thread will bring you is mini modeling and that's not even related to peroxide use
Before guessing and dumping anything into that reef, have your invader + test rock in a bucket getting your scaled down doses of chemi clean, vibrant, anything you hope the whole tank complies with
What works in the bucket is ok to apply, we should never use our whole reefs as a testbed when full rip cleaning cannot be done (rip cleaning is the only safe move that never kills tanks) all other moves change your nutrients though the corals might like current params, and commoner methods subject the entire tank + non targets to the treatment, this is why corals bleach in some treatments but they never ever bleach or die in rip cleaning threads, large tankers have tough choices to make in the midst of an invasion but mini modeling still is better than the common way of dose n hope
