Chaeto needs to be part of a long-term plan. If N and P are too high, it will not grow every well, if at all, so you have to find some other way to get them down. A second skimmer can help, if you have the room. So can water changes or more real live rock... or just time for dead/dry rock and dry sand to get some anoxic areas to turn no3 into nitrogen gas.
Chaeto takes work, but not much. It needs pruned or else it will slow down. It can use up all of the iron and some other traces and also quit growing - you need to still change water and/or even dose iron if you want to grow chaeto.
For my tank, real live rock, 3 inches of sand, three skimmers and fuge full of chaeto keeps my N around .1 and P around 1-3 ppb. I change some water too. I feed a LOT and also export a LOT. Corals grow like crazy. It is kind of a self fulfilling prophecy where the lower residual levels allow the chaeto to grow faster.
I get this much out of my 10g fuge ever few weeks. If I wait too long, it will slow down growing...