# Why not use limestone rocks?



## TWood (Dec 9, 2004)

Our water supply comes from limestone formations. Putting limestone rocks in the tank isn't going to affect the water. I doubt that a little CO2 added to the water will melt the limestone. So why is it 'conventional wisdom' not to use any rocks containing limestone? As long as the the fish and plants are happy, why not? 

BTW, I'm keeping goldfish and simple plants, and they seem okay with it. CO2 at about 1 bubble/second/40 gallons, 2WPG, inorganic ferts.

TW


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## HeyPK (Jan 23, 2004)

Why not?? Go for it. I think that a lot of people who want to keep soft water tanks for soft water fish, such as tetras, etc. can't stand limestone because their water gets hard from the slowly dissolving limestone.


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## plantbrain (Jan 23, 2004)

Every spring filled with submersed weeds in Florida has limestone........

Regards, 
Tom Barr


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## Steve Hampton (Feb 13, 2004)

The biggest reason for those words of caution are due to to possibility of having tank water that becomes several degrees harder than your tap water. When that happens you could have issues with water changes causing a large and sudden change in TDS. Provided you do lots of frequent and large water changes there is no need to be overly concerned with limestone rocks...or if you were to do only a few small changes, then the impact would be lessened too. Changes in pH due solely to CO2 injection are not problematic, changes in pH associated with drastic changes in TDS (GH, KH, etc.) can cause almost instant death for some fish. Like most words of wisdom the context of the cautionary advice has been convoluted over time. Wright Huntley has some of the most logical and insightful comments and posts if you search through the archives of the APD.

Regarding the combination of limestone and CO2...carbonic acid increases the solubility of calcium carbonate significantly...see calcium reactors in Reef Tanks...but still, it really an issue of dwell time.

And the problems are associated with fish not plants...just so I don't accidentally mislead anyone.


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## RedDelPaPa (May 18, 2005)

TWood said:


> Our water supply comes from limestone formations. Putting limestone rocks in the tank isn't going to affect the water. I doubt that a little CO2 added to the water will melt the limestone. So why is it 'conventional wisdom' not to use any rocks containing limestone? As long as the the fish and plants are happy, why not?
> 
> BTW, I'm keeping goldfish and simple plants, and they seem okay with it. CO2 at about 1 bubble/second/40 gallons, 2WPG, inorganic ferts.
> 
> TW


I would say with simple, manual co2 injection, you'd be ok. It will eventually throw off your co2 ppm calculation though. And you sure don't want them if your using a setup with an electronic ph controller. Cause what will happen is, the ph controller will constantly try to maintain your desired ph by keeping the valve open and adding co2 to your tank. The lower ph will cause the limestone to start disolving it's minerals. In turn, the ph controller will work harder to keep the ph down by dumping more and more co2 into the tank. Which in turn, will cause the limestone to disolve faster and faster. You should see where I'm heading with this. Pretty soon, you'd have a disaster on your hands. With all your fish dead, and disolved co2 levels at or near saturation. I can't tell you what the ppm of that would be, but I'm sure it's way way over 25 or 30.


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## plantbrain (Jan 23, 2004)

any changes in ther KH, if not accounted for throws off CO2 readings, if you use a controller, folks need to be very aware of that.

But if you do not use a controller, then the KH changing will not make a difference(unless it goes to 0 and even then it's debatable), you still add the same amount of CO2 into the water.

The rate of Ca++ and alkalinity dissolved and added to the tank is *slow*, we try to use powdered caCO3, stuff takes forever to dissolve............

Regards, 
Tom Barr

www.BarrReport.com


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