[pjf]

I have read the posts that praise the RDSB's ability to remove nitrogen and phosphate from the water column. I have also read the posts that urge an adequate flow of water above the RDSB to prevent it from accumulating detritus and becoming a nutrient sink.

Here's the question that continues to trouble me:

If RDSB's can import nitrogen and phosphate from the water column, how is the same nitrogen and phosphate exported from the RDSB?

With macro algae filters, the anwer is easy: you simply trim the algae to export the nitrogen and phosphate from the aquarium system. What is the equivalent export action with respect to RDSB's?

Are we to assume that garbage just keeps going in with nothing ever coming out?