can i use tap water?

Although it is common to use tap water, I recommend only using purified water for reef tanks!

Tap water has several disadvantages:

  • it might contain unwanted nutritions (Nitrates, Phosphates)
  • it might have harmful substances within (iron, copper, lead, …)
  • Trace elements like Ca/Alk/Mg are already in the water. Mixing water for water change with salt mixtures will ADD this trace elements again and thus be “to high”
  • Variations in water quality are typically between seasons 0. At winter most water works add silicates 0. At summer often chlorides are added
  • Sedimentation of your houses piping might reach your tank

For most tanks a reverse osmosis unit (RO) with additional water purification (silicate filter) is a good choice

  • RO: removes nearly all unwanted material on a mechanical way
  • Silicate filter removes silicate still remaining after RO as well as further substances on a chemical way

There are more options of water purification that might be interesting for big tanks. For small/Nano tanks usage of distilled water is also a good option.