I know limestone leaches - but I have used a peice for a handfull of years in a ciclid tank. How much can it leach and how much can it effect the water if I am doing 1/2 water changes weekly.

Just wondering if ei has made the limestone arguements a little less pervasive.

Mostly wondering because if I ever did a local biotype - limestone is pretty much it
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could not help but think of doing a local biotype after a hike I had this last weekend.

Good point. I guess it wouldn't hurt to try. How much can it leach? You may be surprised but its worth a shot. Keep in mind that the impact on water hardness is dependent on the competence of the rock (ie. it will vary from formation to formation.)

Another thing to keep in mind is that limestone will alter not only the GH but KH as well, making it difficult to determine your CO2 concentration.

Other thing I am considering - my tap water ultimately comes from a limestone lined lake. That water has so much desolved calcium in it it might actually make my current rock grow .

I have been remiss on actually testing my current water, but lfs guy who lived about 1 mile from me mentioned it was pretty (err vary) bad. But then again he was probably trying to sell an RO system.

What? How? Where did you learn this? Can you back this up?

Limestone will affect kH. But since it adds Bicarbonates it doesn't mess up the CO2/pH/kH chart.

I know that starting with my tap water with basically 0 gH and 0 kH that I can place half a cup of crushed coral in my canister filter and have water with a gH of 17° and a kH of 11° in 7 days.

Sorry, my bad. I was thinking of something else. Thats what I get for trying to make a quick post when I'm supposed to be working.

Rex, I can see exactly where Clone is coming from. While it doesn't affect the charts, it changes the Kh, meaning your last test is no longer accurate. Where is your CO2 in the above example on day 2? Day 3? Day 4? It is "difficult to determine your CO2 concentration" without testing Kh daily, as the Kh (which I assume you meant) moves from 0-11 degrees over a 7 day period.

But it's not difficult. You do a pH test a kH test and look at the chart. See, not difficult, just changing.

If you assume things we all know what happens.