The new or not so new aquarist may be puzzled by the repeated advice to use purified tap water. So tap water is purified, use that. No.
The water coming out of the tap is purified by the local water authority. Regulations advise the amount of additional substances that are permitted, and, hopefully, the water authority meets that criteria. However, this is for human consumption. We can tolerate an amount of nitrate, phosphate, heavy metal such as copper etc. Obviously we can, we drink it, and clean our teeth with it. Our children do likewise. So what is this need for purification of the tap water for use in a salt water aquarium?Read more →