Honestly you could just stick a light in an empty chamber and it will grow algae.
If the light is powerful enough, it may be able to counteract the algae growing in your display. You don't necessarily have to add much macroalgae.
The point is to give microalgae a place to grow instead of your DT. Of course places to hide will be beneficial to hosting copepods down there, but you don't want too much macro algae that will out compete micro algae which the pods will eat. So this all really depends on your goal.
Are you looking for copepods, isopods, amphipods?
If the light is powerful enough, it may be able to counteract the algae growing in your display. You don't necessarily have to add much macroalgae.
The point is to give microalgae a place to grow instead of your DT. Of course places to hide will be beneficial to hosting copepods down there, but you don't want too much macro algae that will out compete micro algae which the pods will eat. So this all really depends on your goal.
Are you looking for copepods, isopods, amphipods?