yes fresh water ..VERRY few times it happens but we do get 2 or 3 dead bass at our tx over a year and as not wanting to waste i clean and chunk for my fish accually my yellow tang is the most agressive with it often they will have row i have not saved tell a few weks ago i decided to save a bass row froze the whloe sack and cut verry small piece off to feed so far the fish and anemone luv it just make sure not often and SMALL amounts