Water Conditioner: What It Actually Removes

The bottle everybody buys and few people read.

Chlorine and chloramine

Municipal water is treated with one or both. Chlorine gasses off if water stands; chloramine does not, which is why standing water overnight is not a substitute for conditioning.

Heavy metals

Most conditioners also bind trace copper and other metals picked up from pipework.

Dose for the volume you add

When doing a partial water change, dose for the new water, not the whole tank, unless the label says otherwise.