actually, the live rock or crushed coral or even better, dead coral skeleton will not cause a waste build up. its the complete opposite. its an organic solution to detritus in your sump & DT. i'm passing on knowledge i acquired from a water treatment engineer, which constantly stresses to use a complete organic system. the key is finding enough dead coral skeleton, not dried up, but skeletons of freshly dead coral. according to him, they contain microbes that feed off of detritus that should be placed in the first chamber of the sump. its similar effect to bio balls or that media that looks like coco puffs, but with actual live marine microbes that lives symbiotically within the coral skeleton, which feeds off of nutrient rich water. but again, that's my experience with going more organic & advice from an engineer with tons of experience, thats what he went to school for & does day in & day out for a living. good luck & happy reefing.