This article is from the Beginning Fishkeeping FAQ, by Thomas Narten with numerous contributions by others.
In addition to the additives described above (chlorine and
chloramine), municipal water may (or may not!) contain other elements
that the aquarist may need to know about. Water in some locations
actually contains nitrates. In some places, water contains elevated
concentrations of phosphates (1 ppm or more). High phosphate has been
linked to algae problems, and a comprehensive algae control strategy
may require removing phosphates. High levels of iron (1 ppm or more)
have also been linked to thread algae. Consult the algae section of
this FAQ for more details.
 
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