Every reef tank comes with its ups and downs. For the past month I have been battling Bryopsis. My nutrient levels are very close to 0. It is a 20G IM Fusion. I have been doing larger weekly water changes and manually taking the algae out by hand. It grows back within a week and it grew on the outside of my tube worm exit I guess preventing it from coming out to feed and killed it. Now it is growing on the bare spot on my Gonipora. Ca,Kh,Mg,salinity,PH are all within levels. Any ideas why they grow?