Yes big GHA problem; been manually working on it for a 1.5 months and it used to look a lot worse, which is hard to believe.You have a bit of Green hair algae expolsion here. After you have reduced or rid the tank of aptasia,
Then reduce white light intensity and number of hours of white lighting and add some snails such as :
Astrea
cerith
turbo grazer
trochus
A Pencil urchin
8-10 Caribbean blue leg hermits
Are you using RODI water or tap water from the faucet ?
What is your phosphate level?
Is tank at or near a window?
My original CUC snails dwindled and I left these phosphate remover pads that came with my Fluval 407 canister filter in the fluval for almost a year. I‘m guessing they had been leaching phosphate back into the tank for a long time and GHA has gotten out of control. So I now have some Trochus & Turbo snails, a tuxedo urchin, a foxface, and a lawnmower blenny in quarantine to help me battle algae (fish are in separate QTs from the inverts).
Yes, using RODI, but need to get new filters as they are aging.
Phosphates read near zero, but using the API test, whose first color change above 0.00 is 0.25 (i.e. not very specific). Nitrates are ~ 5. Clearly there are phosphates in my tank, I think I’m one of those tanks whose phosphates immediately get take up by the growth of new algae.
Tank near a window? Affirmative!
It would be nice if my rock looked this again (Jan 2022)
And also the Macro algae was quite nice compared to the GHA (May 2022)