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Why is my (soft) tap water becoming hard in the tank?

Discussion in 'New to the Hobby Questions and Answers' started by no_robotocha, Mar 6, 2019.

  1. no_robotocha

    no_robotocha New Member

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    New to this and new tank - after weeks of prep, finally have neon tetras in.

    Testing the water, all seems fine except for the water hardness, which is measuring at the hardest on the scale (180).

    We tested our tap water and this had a very soft measurement (20).

    We now have a new tank filter installed and some other measures to take (not re-tested yet) - but does anyone know what factors may be causing this issue?

    Thanks in advance!
     
    #1 no_robotocha, Mar 6, 2019
    Last edited: Mar 6, 2019
  2. Byron

    Byron Member

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    Probably there is some calcareous substance in the tank. This refers to rock, stone, gravel/sand, shells, coral, which are all composed of calcareous mineral, most usually calcium although magnesium is often included. These items will slowly dissolve, adding calcium/magnesium to the water, thus raising the GH.

    Rock/substrate made from limestone, marble, dolomite, aragonite, and/or crushed coral can all do this.

    Water is one of the most soluble substances on the planet, so it readily assimilates minerals and organics with which it comes into contact. This is what gives water its degree of hardness.
     
  3. no_robotocha

    no_robotocha New Member

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    Thanks for the response Byron - that being the case, should I be looking to remove these elements (as the recommended water hardness for neon tetras is considerably lower than my reading)?

    As the filter has been added it may reduce levels but I don't want to endanger the fish..
     
  4. Byron

    Byron Member

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    The filter is not likely to reduce the GH. Assuming there is something calcareous in the tank, it needs to be removed. If all objects are inert the GH of the source (tap) water will remain basically the same in an aquarium, though it may lower depending upon initial levels and organics. But that would not bother soft water species.

    Can you think what might be doing this? Are there any rocks/stones? What is the substrate material?

    What is the media in the filter? This can increase hardness if again there is something calcareous dissolving, though that is unlikely the issue here from what you've posted, but it is worth pinning down. Water chemistry is a very complicated business, because one factor can affect others; keeping things simple is always safer.
     

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