More Reading....I know its lengthy but this article should help you out tremendously.
MORE ABOUT KH:
Another consideration of KH is that you can generally safely add the buffers (both freshwater and saltwater) that effect KH without sudden changes in chemistry (unless your freshwater KH is under 50 ppm already), unlike a direct ph or GH change. Maintaining these KH buffers keeps your tanks pH from drastic swings which can be deadly as once alkaline buffers are depleted sudden and dangerous pH crashes are likely (see more about pH later in this article).
The chemistry behind KH is quite complex, so I will not go into detail, however in the most simple terms I can think of; is adding these carbonate (or bi-carbonate) buffers will raise pH to a point of stability and the continued use of certain carbonate buffer “mixes” may raise pH even more (which is why a KH of 50 ppm is all you would want with your discus, while a KH of 200 plus is recommended for African Cichlids or Marine Fish). The rise in pH is related to the ratio of H+ to OH- ions. The CO3- will react with the H+ and eliminate it. This reaction will cause more H20 to break up into H+ and OH- ions. Because some OH- ions were already present, this shifts the ratio thereby raising pH and making the water base (alkaline).
Putting it another way; KH (carbonate hardness) is caused by metals combined with a form of alkalinity. KH (or Alkalinity, which is the more technically correct term) is the capacity of water to neutralize acids and is caused by compounds such as carbonate, bicarbonate, hydroxide, and sometimes borate, silicate, and
phosphate. In contrast, noncarbonate hardness (GH) forms when metals combine with anything other than alkalinity.
Carbonate hardness is sometimes called temporary hardness because it can be removed by boiling water. GH (noncarbonate hardness) by comparison cannot be broken down by boiling the water, so it is also known as permanent hardness.
Baking Soda (Sodium Bi-Carbonate HCO3-), is often used for KH, Sodium Bi-Carbonate will buffer at 8.0 to 8.2. Just a little Sodium Carbonate will absorb free H+ ions, and this causes alkalinity (which is the lack of H+ ions).
To stop the Sodium Carbonate ions from consuming too much H+ and to keep a pH of 7.0 we need to restrict the amount of Baking Soda used, as it is always looking for H+ ions to consume. This is why I prefer using products that not only contain sodium carbonates (or sodium bi carbonates), but the proper ratios of other minor elements such as
calcium and
magnesium. Sea Chem Buffers; Marine, Malawi, Victoria and to a lesser degree; aragonite, Seachem Cichlid Salts and Mineral Blocks are examples of preferred methods for KH maintenance.
Crushed Coral/Aragonite
Aragonite or crushed coral is sometimes employed for KH and GH stabilization, however aragonite and crushed coral (as with Wonder Shells) only stabilize KH (they are poor buffers, especially crushed coral) and should not be used in place of a true KH buffer such as Sea Chem Alkaline Buffer when true buffering is necessary due to fluctuating KH or pH whatever the cause may be.
Crushed Coral is primarily made up of Calcium Carbonates (CaCO3) and has VERY LITTLE bicarbonates while Aragonite is of similar make up, but has a much better surface area for dissolving of minerals making it a better choice of the two.
Aragonite is useful at stabilizing a higher kH of around 240 ppm or more, which is the minimum KH (alkalinity) needed for Marine Aquariums, but does not respond to changes rapidly enough when carbonic acids are produced at a rapid rate in an aquarium (usually a high bio load or large amounts of organic mulm will cause this). Even in marine aquariums with aragonite, this may not always be enough to maintain a proper KH (alkalinity) level, especially in tanks high bio loads and without adequate water changes (even skimming can remove some elements). What Crushed Coral are better for is necessary minerals and in the case of Aragonite, it generally has a few more minerals in higher concentrations such as the important mineral (for corals), Strontium.
HOWEVER it often takes copious amounts of acids to free these minerals and what little bicarbonates/carbonates that are available (which is where a
calcium reactor is helpful in marine aquariums), which is why use of these “gravels” (technically these are coral skeletons) should be used in a “Filter Bag” to “release” these minerals when used in Freshwater, especially African Cichlid aquaria. The use of a filter bag in a high flow area will improve the dissolution rate releasing more minerals and allowing for some buffering, although again I will point out not a lot due to the mineral make up of crushed coral (Aragonite will do a slightly better buffering job when employed in a filter bag).
This said, despite the popular use of crushed coral for pH/KH control in African Cichlids, it is a poor choice for this, especially in high bio load aquariums do to the FACT of its mineral make up (you CANNOT make a mineral appear out of nowhere that does not exist and that seems to be what many mistakenly believe when using crushed coral to increase KH/pH), this is an unfortunate “urban aquatic myth”.
The bottom line is that Crushed Coral or Wonder Shells MAY help maintain KH/pH in a low bio load aquarium, they are best used for minerals (GH) and even here the Wonder Shell is far superior do to the fact it dissolves at a much faster rate and reacts much quicker to chemistry changes in the water than does crushed coral.
Besides the simple mineral makeup of crushed coral, my own tests (especially in marine aquaria) show that its use to increase KH simply is poor!
thats more than I know and thanks for the help ....I learn something new everyday here!
