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What type of rocks will not affect hardness

1129 Views 6 Replies 6 Participants Last post by  Zapins
Hi there,

I was wondering what type/sort of rocks do not affect water hardness. What should I look for?

To test them can I use hydrochloric acid (spirits of salts we call it here) or at least my dad does

Regards darren
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Granite is always good. Most rocks with lots of holes in them are not good, with the exception of lava rocks. I don't recall a black rock that wasn't good.
1 - 1 of 7 Posts
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