gh & kh??

[schizo_fish]

what is the importance of gh and kh in a freshwater aquarium? and what would be a recommended reading for these?

 

[K-Holed]

It all depends what fish you are trying to keep and whether or not you are trying to breed them.

gH = General Hardness. This is how 'hard' or 'soft' your water is. Usually you find that acid water tends to be softer than alkaline water. Many South American fish prefer soft, acidic water where as Rift lake cichlids prefer hard alkaline water.

kH = Carbonate Hardness. This is the buffering capacity of your water. The higher the kH the more resilient your water is to fluctuations in pH. Its like a sponge, giving your water the ability to 'soak up' anything that might alter the water chemistry.

kH, gH and pH are all conected in one way or another, it's difficult to change one without affecting another. Messing around with water chemistry can be a tricky buisness and unless it can be done in a simple manner (e.g. peat/bogwood to lower gH and pH) or you -need- to achieve certain parameters for breeding and the like, it's better to leave it the way it is.

 

[impur]

The hardness of water is related to the dissolved minerals in contains. The total hardness is usually regarded as consisting of two components: general hardness (GH) and carbonate hardness (KH). General hardness is caused by divalent metal ions, primarily calcium and magnesium. Carbonate hardness is due to carbonate/bicarbonate ions, and represents the main 'buffering capacity' of the water, i.e. its ability to resist pH changes. KH and pH are therefore inter-related: if KH is high, the pH will be very stable (and difficult to alter), if KH is low (e.g. less than 3 degrees KH) then the pH will be less stable.

Carbonate hardness is sometimes referred to as 'temporary' hardness, because it can be removed by boiling, which precipitates the carbonates. The remaining hardness contributed by other salts of calcium and magnesium is then referred to as permanent hardness, or non-carbonate hardness.
Note that a confusing number of units have been used to refer to hardness values, including different English, American, German and French degrees of hardness!

Increasing hardness is normally fairly easy. Adding decor to the tank which will gradually leach hardening salts (such as limestone rock) is one way. Hardening materials such as coral gravel could also be added to a canister filter. There are also commercially available hardening salts - these are often used for tanks containing cichlids from the African rift lakes, which are hard and alkaline.

Decreasing hardness can be done in two main ways: dilution with softer water, or adsorption of hardening ions. Some people use reverse osmosis (RO), distilled, deionised (DI) or rainwater to dilute their tapwater to a hardness suitable for their fish. Note that hardness has a fairly straight-forward relationship with dilution. For example, if your tapwater has a GH of 10 and you use half tapwater and half pure water, the GH will be 5.
There are also specific products designed to reduce hardness by absorbing the hardening ions. One natural product which can achieve this is peat, while also adding beneficial organic acids to the water. However, the quality and usefulness of different types of peat varies considerably.

Note that normal table salt (sodium chloride), does not increase hardness. Although it will increase the overall mineral content of the water (and its 'ionic strength'), it is not a hardening salt, like the salts of calcium and magnesium, so will not be measured by a normal GH kit.

Reading:
http/www.myfishtank.net/articles/waterquality.php
http/www.drhelm.com/aquarium/chemistry.html
http/faq.thekrib.com/begin-chem.html
http/fish.mongabay.com/chemistry.htm
http/www.chelonia.org/Articles/waterchemistry.htm



That should get you started. HTH!!!