Halimeda keeps being brought up, so I guess it’s appropriate to share experiences with that too (Spoiler alert, I love macro and tried growing a LOT of it in my display tank with lots of different results). So the Halimeda used to come in a LOT on premium gulf rock, and one of my tanks was started with that. At first, it didn’t grow real well, but I upgraded my lighting from regular fluorescent lights to VHO’s, and it bumped up fine after that. But when I swapped in metal halides, it EXPLODED. Halimeda does need a bit of light acclimation at first, but when you can ramp it up pretty fast. The problem I had with it was that it consumed soooo much magnesium and calcium, I lost my montipora colonies and had to restart them from fragments of the original colonies. It was growing way faster than the corals could, and even with a calcium reactor, it stripped calcium and magnesium faster than the montipora could keep up with. My acros survived, but I lost 6 year old montis.
I ended up ripping out the halimeda, and tried the feathery looking caulerpa taxifolia. That stuff turned out to be even more prolific than the halimeda, which was saying something since I was stripping 2lbs of halimeda weekly from my tank and refugium (which had only PC lights on it). At one point, it went sexual, and I had to do a mad dash of water changes and carbon, while ripping out huge wads of caulerpa and cussing out my planted reef tank schizophrenic aspirations. I ended up having to go through the tank with tweezers to try to remove every single strand of the caulerpa, because it was insanely well entrenched on my rocks. It still came back in little patches (as did the halimeda) for years, but as long as I kept it trimmed way back it didn’t cause more problems.
For a FOWLR the halimeda would probably be fine. I wouldn’t ever put that feathery caulerpa in another tank again unless I was going to dedicate a portion of each night to trimming it.