# Water Hardness and Limestone/Live Rock in the FW aquarium



## JoeG (Jan 5, 2011)

SO I have been looking into the use of Limestone and/or Live Rock in my FW aquarium. Since I am in Florida, it is readily available and, more importantly, i like the look. I understand that these rocks will increase the hardness but I am wondering to what degree, if any, and how predictable this can be.

So for me, my water is already hard enough to leave scale sand in the bottom cold water tanks (like a toilet tank) without any heat to cause thermal decomposition. Now I have not had a formal test done, but i will, to see what my levels are, etc..

Now my question is more to the point around the need of understanding the saturation index and if this could be used to predict the max saturation any CaCo3 based rock(s) could cause. My research lead me to a formula called the "Langelier Saturation Index (LSI)" which is used to calculate a number used to predict the calcium carbonate stability of water. Does anyone take this kind of approach? Is it overkill? I just dont want to kill my future fish with unstable water.


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## Franco (Jun 25, 2010)

If your water is already hard then don't worry about it. The limestone will only start to dissolve/leach carbonates if the water became softer for some reason. It an equilibrium thing. I use limestone for caves and attached to the base of driftwood in my tanks and it has no affect. I can find it in nice 1/4 inch thick plates and its really easy to drill so its great for using as a base on large wood pieces.


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## JoeG (Jan 5, 2011)

I was hoping to hear something like this, and it made sense to me but wanted to make sure first. My local Lowes Home Center had some large (10-12"+) rocks called "florida limestone" which are actually live rock...for $4.50. Think i will be jumping on that!!


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## Michael (Jul 20, 2010)

The only probelm I can see is if you have your heart set on fish that need soft, acid water.

I'm curious, what exactly is the "live rock" that Lowe's is selling?


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## JoeG (Jan 5, 2011)

dead coral rock. Its pretty common down here as well as limestone but there are some obvious visual differences. A lot of people use larger chunks as landscaping stone, though I never really cared for because everyone seems to do it.


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## Michael (Jul 20, 2010)

Oh, is that the beautiful stone that often has circular depressions and holes in it? I've seen it on my visits to Florida, and admired it.


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## JoeG (Jan 5, 2011)

yes. Generally it can be limestone but if you look closer, and you can see the coral structure then its coral rock.


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## Diana K (Dec 20, 2007)

As above, if your water is already GH and KH over 10 degrees, even as high as 20 degrees, then adding rock or coral will not make much difference. 

These materials vary a bit, but most will dissolve when the water is more acidic, and not dissolve when the water is more alkaline. pH usually settles in the upper 7s to low 8s. 

This is too hard for many of the soft water fish unless they have been bred in captivity for many generations, but is just fine for Livebearers, many Rainbow Fish, Rift Lake Cichlids and some other fish. 

This is a good example of working with your tap water and going with what it is best suited for.


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## JoeG (Jan 5, 2011)

I pulled our county tap water report and depending on the source, hardness can be between 8-11 grains per gallon or 153-210ppm. And I agree, working WITH your tap water is really the best route but i was disappointed when i found I could not really have a discus tank  without the hassle of R/O which I am not ready for.

In the end, I have decided to go with the stone. I have full faith it will not alter my water chemistry in any dramatic fashion but since this tank will be running for at least 2 months before ANY fish go in, I will have a chance to observe. This has also sent me head on into my design...very excited!! :biggrin:


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