well, i'm basically almost back to square one with my system after an almost 3 year battle to eradicate the several species of valonia that ate my lunch.
i was heavy into macros. i could control everything , even the scary pest ones, but not the valonia. it is indestructible and low nutrient and any amount of light is fine. once it spores, thousands pop up everywhere. they will crowd anything attached to rocks, like shrooms and zoo's get smothered.
my system is stripped down to basically rock + algae blenny and a few hardy stragglers that survived the valonia(like my non-photo stuff in the dark sump heh)
i see 3 of them this morning that i will knock loose and siphon out. i'm hoping the nightmare will be over by march, the 3 year mark and that most of the spores have sprouted or whatever..
from henceforth i will maintain zero tolerance for valonia.
i would recommend you gently roll that thing loose and get rid of it, and any others you see. man i respect the valonia. and have the scars to prove it.