IT ALL DEPENDS ON HOW MANY ORGANISMS ARE ALIVE IN YOUR TANK, IF THERE ARE ALOT THEN LET IT BE, IF THEY ARE SCARCE THEN REMOVE IT BEFORE YOUR AMONIA GOES UP.
IF YOU HAVE SNAILS THEY WILL TAKE CARE OF THE JOB, CRITTERS THAT ARE ALIVE IN THE SAND (IF YOU HAVE THEM) WILL TAKE CARE OF THE JOB. IF YOU HAVE NO CRITTERS AND ACTUAL ANIMALS THEN REMOVE THE CARCASS.