First of all, properly fired LECA is usually dead-on neutral, so the applied solutions and the actions of the plants themselves are what control the pH.
Various chemicals are using in the process of making LECA - binders to hold the balls together in their "green", unfired state, and to create the porosity in the desired form. Sometimes there are residues from them, and often the balls are quenched with non-potable water (sometimes seawater) to coll them down and quash the dust. The addition of the calcium nitrate and/or magnesium sulfate to the soak solution helps extract those residues, and leaves behind plant nutrients.
Magnesium sulfate does not affect the pH appreciably, which is why it's a great addition to fertilizer for magnesium enhancement.
If your medium is too high in calcium, it is unlikely that any acid treatment will lower it sufficiently. I was just questioning (hence the soak) if it was from the manufacturing residues.
Last edited by Ray; 12-25-2010 at 11:05 AM..
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