Chaetomorpha, a very popular macroalgae for use in saltwater aquarium refugiums, is a great nutrient absorber. However, this macro grows in a dense, round ball. Because of this, the underside of the algae doesn’t get enough light, and often dies in the long run. This of course released any absorbed nutrients back into the aquarium from which they came. To prevent Chaeto from dying, try using water flow to slowly tumble the algae. This will keep all sides of the plant illuminated, thereby preventing its death. A small water pump can be used to tumble the Chaeto, or you can tee off part of the return pump to create more water movement in the refugium.