To maintain balance in a saltwater reef aquarium with a sump and refugium, the macroalgae needs to be thinned out/pruned/harvested periodically. As the algae uses up nutrients (food, fish waste, phosphates, etc) available within the water, it should grow, provided it also receives adequate light. I run a grow bulb 24/7 and have gracilaria, chaetomorpha and ulva growing. This algae provides refuge for many copepods and amphipods, which propagate and offer food for the fish in the main aquarium. I have been having some challenges with cyano bacteria and hair algae in the main tank, so aside from reducing the lighting, performing water changes and overall maintenance, I have been harvesting the macroalgae out of the refugium area of the sump.
