I'm just now seeding my old rock for a new tank i'm setting up. I can't donate just yet, but i'd love some rubble from different tanks to seed my old dead rock! Also need some chaeto preferably for the refugium. I know you said you had caulerpa, but i don't think i will ever put any variety of that back in my tanks. I had a grape explosion that i could not eradicate!Proposition here. I think we all need to occasionally give each other some type of rubble or sand (preferably both). We all likely get coral, rock, water and sand from different places. Your tank needs as much biodiversity as it can get.