If it is the DOC from the chaeto you want specifically, stressing the chaeto will cause more DOC to leak.I add algae water I grow or tank water to level on blender. I strain small pieces of macroalgae, dosing unit cannot work, if small pieces not removed.
To stress the chaeto -
1. remove some chaeto from your fuge & let it dry out a bit- to replicate low tide.
2. Re-immersing the chaeto is another stress, especially in fresh cool water (RODI).
3. Leave the chaeto in the RODI for 30 minutes, & then blend, in the RODI water, & add the RODI water to the dosing solution.