I have kept aquariums for over 50 years (yes I am OLD) I now have a 125 which I call my nano, I am using triton and bought some new macro algae, a week later thousands of the red pesky beasts, My corals were turning black some large colonies had died , fish were OK, I doses flatworm X and wow was I surprised, the water column was rusty colored thousands of the pesky beasts came out of no where the skimmer skimmed nasty orange skim mate, and I very quickly placed a Hugh reactor with about 4 pounds of carbon in the refugium, I removed all sand and after a few hours I placed a vortex diatom filter, and a few hour after that the water column had nasty strings of slime from corals and very cloudy. I changed 70 gallons of fresh sea water placed the vortex diatom filter again, Left it over night and hoped. I decided to remove the carbon and replaced it, I completed another 70 G water change and dosed with fauna marine bacteria. l, removed several dead corals and three days later another large water change. The tank is now amazing several corals lived, no further out breaks and my fish all lived. The diatom filter pulled out loads of nasty gunk, My learning curve here is to treat the macro algae with coral dip, and just know that strict observation of the corals and tank is essential especially when the skim mate turns orange