Im a bit nervous taking my carbon out. I dont know how many threads of dead fish where the person didnt have an explanation about the fish death. Recently some guy had a full tank failure and loss everything. Everything was right in the tank (Water Parameters, temp etc), and still couldnt figure it out. I was thought his water became contaminated somehow. Its always possible somethng could get in your water, from the tap, from something on your hand, or something else accidently. So I dont know, I'll keep my carbon in for safety. I think alot of these unexplained deaths happened because no carbon was in the tank. I know some people dont use it and are careful, but the chance is always there.