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Re: GH, Alkalinity and CO2 needle valves

> From: Matt Rhoten <mrhoten at oz_net>
> 
> 2) What Tetra says is KH is really alkalinity, and some factor other
> than carbonate hardness raises the alkalinity in the collection
> water. If this is the case, which other compounds (presumably
> hydroxides of some metals or other) are present?

Alkalinity is not a precise term. It can refer to pH (hydrogen ion
concentration) or to the presence of alkali metal elements:
Na, K, Li,... or even the alkali earth metals: Be, Mg, Ca,...n
Paraphrasing from "Aquarium Plants Manual" by Scheurmann which
has a good explanation of the subject:

Total hardness dH (which I think means general hardness)
measures the milligrams of calcium or magnesium oxide in a liter
of water.

Carbonate hardness dCH, is a measure of carbonates: hydrogen
carbonate and the calcium and magnesium carbonate salts.

Noncarbonate hardness refers to permanent hardness from compounds
such as calcium sulphate, magnesium sulphate and others.

To confuse matters slightly more, aquarists add sodium bicarbonate
(baking soda) and calcium carbonate to alter the carbonate
concentration which is also affected by CO2 concentration.
Still confused? Me too.

> One other more mundane question that came up has to do with setting up
> CO2 from one welding tank to more than one aquarium.

Ahh, an easy question. How to minimize the number of expensive needle
valves when "ganging" up on a single tank. Simple:

Tank --- regulator --- needle valve --- gang join --- cheap valves

The regulator reduces pressure to something the needle valve can
properly regulate (~50psi) which then throttles it back to about .5
psi which is easy to balance with the cheap plastic or brass valves
used for running multiple aquarium bubble toys and aeration stones.

Steve