Just throwing out an idea here, but why couldn't agoutihead strain the sand out of the CC, put that sand back in and then just add more sand? Not do it all at once as to release all the gunk in the CC, but maybe a little at a time. I don't know if it would work, or if it would remove all the good stuff in the process, or if disturbing the CC that much would crash the whole thing.
Don't try it yet, I may be out in left field, but it was just something that popped into my head as a possible solution. Anyone have any thoughts on this?