[Timfish]

Well, to start with de Goeij showed inorganic nitrogen and inorganic phosphate was being converted from DOC sources in minutes not days or weeks. Also the cryptic sponges are only feeding on the labile portion of DOC released by algae and corals. The majority is refractory DOC (~ 2/3) and is not being consumed by sponges, at least not in the time scale de Goeij did his experiments. (This refractory portion is why we have to do water changes.) As pointed out in the research posted by Louis Z a lot is sequestered but de Goeij showed these sponges should be growing by something like 30%-35% on a daily basis but they're not. What they are doing sloughing off cells at a tremendous rate (cells splitting in 5 1/2 hours) and the nutrients in this cellular detritus finds it's way into filter feeders in hours.