Carbon in my saltwater reservoir good or bad?
 

I have a plastic drum which I use for a salt water reservoir. Inside I have a heater powerhead and a bag of carbon. My thoughts were to keep the water clean but a friend told me it may pull trace elements from the water. Does anyone know if the carbon is good or bad?

If there's nothing in the water to pollute it, there's no reason to need to keep it clean. To keep it fresh all you really need is to keep it aerated, which can be accomplished either with a powerhead that keeps the water moving, or an air stone.