I’ve been battling GHA for a few months now and It’s upsetting because I got it on a frag plug from my LFS. It has only spread a little bit and it pulls off easily so my nitrates are >5ppm and phosphate is around >0.15. I have tried flipping rocks upside down to cover the GHA, manual removal, turbo snails (worked but didn’t eat all of it) and an emerald crab. Now, I’ve just set up a mini refugium in hopes of it out competing the GHA. A blackout would probably be the last resort because I don’t want to kill any coral