From my own experence, the gracilaria started to grow quickly and then after a while parts of it started to turn white and it gradually fell apart. Some of the fragments found some places in the shade and started to grow again, but after a while they also started having the same problems.
From a internet search I found that at least some of the species of gracilaria that they try to aquaculture for food in natural sea water seem to have the same problems.
You talkin to me? Dont know what species just that they are Gracillaria. They are in a 35 gal tank with 1 65 watt LOA fixture, and low to moderate flow. I dose iron, and KNO3. This tank is connected to a larger system where I have some fish and a suncoral and I feed heavily.