"When the pH in your aquarium falls below 8.2 aragonite begins to dissolve...."

[sjm817]

This is on the Carib-Sea website and seems contrary to what I see posted about the subject of the buffering capabilities of calcium based substrates.

Thoughts?

Why Aragonite?
So what makes aragonite the perfect marine substrate? When the pH
in your aquarium falls below 8.2 (the pH of natural seawater), aragonite
begins to dissolve releasing calcium (great for growing coral and for
water hardness), carbonate (your buffer), and beneficial trace elements
like strontium and magnesium. Your pH comes back up, and the tank
stays healthy, without ever adding a single chemical. Other types of
calcium carbonate don’t react until the pH is in the mid 7’s, which is
lethal for many forms of marine life. In fact, aragonite holds the highest
pH of any gravel or sand, and has up to 30 times the buffering capacity
of dolomite, calcite (so called “crushed corals”), or oyster shell!

[bertoni]

The buffering value of the sandbed is near zero. I have had aragonite substrates from the start, and they certainly don't prevent low alkalinity. It's just advertising. There are lots of threads discussing the solubility of aragonite in seawater, if you want details.

[Serioussnaps]

BS

[Boomer]

BS, aragonite does not go into solution until the pH is in the mid 7's. Most fresh calcium carbonate surfaces actually lower the pH, it is a function of solution kinetics and there is endless data to prove it. The only time such carbonates go into solution at those pH's are very fine dusts or the sharp points on grains. Finally, organics and bacteria will start to grow on them and any such surfaces will do nothing. It has been prove time and time again these or any carbonates do not do any buffering accept at times when it is fresh and usually that is only Puka shells.