It’s easy to assume that illuminating the macroalgae in your refugium for 24 hours consecutively would lead to fast growth and therefore lower “nutrients” in the water. While it may be true, it would probably only be short-lived. Macroalgae, like Caulerpa and Chaetomorpha, use photosynthesis to create food for themselves, and effective photosynthetic processes require periods of darkness. We won’t get into all of the biochemical reactions that are taking place, but the take home message is that you should provide some period of darkness for the whatever macroalgae you use, as it is a more natural approach. Besides that fact, constantly illuminating your refugium could lead to the algae “going sexual”, a process in which it is believed that stressed out algae dissolves and sends spores or some other substance into the water.