Re: CO2 Questions

> From: Matt Rhoten <mrhoten at oz_net>
> Date: Sun, 01 Oct 1995 23:40:46 -0700
> Subject: two qs: KH/GH, and CO2 valves
> In the Tetra _Dwarf Cichlids_ book (ISBN etc available on request),
> the authors list the water conditions in a number of fish collection
> sites. Many - I won't say "most" - of these tables note a GH lower
> than the KH. For example, 3.9dKH, 1.9dGH.
> I understand that GH measures Ca++ and Mg++, while KH measures CO3--
> and HCO3-, and that these values don't necessarily go in sync. As I
> see it, this could happen two ways:
> 1) Some other cation is there instead of Ca or Mg. This could happen
> with the presence of, for example, our friend sodium bicarbonate. If this
> is the case, which ions? Na+? K+?

Well, it can be ANY carbonate salt other than CaCO3 and MgCO3.  If it's 
sodium bicarbonate, then it's Na+. (duh, he says).

> 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?

Phosphate buffers, tannic acids, etc.

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

> My hypothesis for how I will need to set it up involves having only
> one regulator for the welding tank, but one needle valve per fish
> tank. So there would be a Y-joint 'after' the regulator, and each
> needle valve (one per aquarium) would attach to the Y-joint. Is this
> how it's done?

I tried it "the other way" and quickly learned by the results that you 
need to trust the laws of physics.  You are exactly right.  One regulator.
Tee joint (cheap), multiple needle valves (expensive).  Only real way to 
keep one tank from "feeding back" to the other one.  I suggest finding an 
inexpensive needle valve supplier (ie, an alternative to the Nupro-S series).

Good post, btw.

    - Erik

Erik D. Olson					              I'm baaaack!
eriko at wrq_com (was olson at phys_washington.edu)