What you are looking at is about 2 weeks of caulerpa growth in my display tank that I discovered shortly before MACNA. I assume it came from an external refugium I broke down last month after a year without issue oddly enough. Caulerpa in my display tank was a serious red flag. I knew I had to deal with it fast or it would take over the tank and waiting this long was dangerous. I took out the offending rock - a nice piece of Indo - and grimaced. I knew what was coming; saving the rock was futile. It was porous, textured and the caulerpa had its roots dug deep. I took it out on to the driveway and chiseled the acropora off it. Most of the caulerpa went into the freezer. Hopefully this is the end. I can always replace the rock, but the whole tank would be a bit much. Dipping the rock in liquid nitrogen would have been a cool way to kill this caulerpa... until I found out how much a bottle of liquid nitrogen cost.