Re: [GSAS-Member] CO2 Question

[macker <macker@gmail.com>]

Neat,

All great points. It is true that that you need to recalibrate, but
typically not after every water change. It seems to drift about every 3-4
months w/ continuous use, and just use simple PH 4 and PH 7 solution does
the trick.

Never4 had a problem w/ tannins desolving, always seemed to adjust for that,
but the tank was heavily planted which I think gives more leaway.

One thing I have never been able to control however, is hardness. Very
annoying, and its such a crucial piece of the puzzle. Even with a few
crushed oyster shells ina  bag in teh filter, it was always too much, or not
enough, sigh.

Thanks for the info

On Mon, Oct 19, 2009 at 1:47 PM, Erik Olson <erik@thekrib.com> wrote:

> On Mon, 19 Oct 2009, macker wrote:
>
> > That works too, a steady bubble. Never worked well for me bc we travel a
> > lot, 4 day stretches, etc. One thing gets out of balance, and Ive seen
> some
> > messy things happen. Maybe its just my controller or something, you guys
> are
> > smarter than me, but it regulates the PH 24/7 to 1/100th of the set PH,
> > turning off or on, basically a digital tank that can correct its own
> errors
> > without human interference, and time of day. It smoothes out a single
> > fluctuation instantly.
>
> Couple things.  The fact that a probe reads three digits doesn't
> actually mean those digits are accurate.  Remember also that the system is
> really regulating the pH, not the CO2.  As the chemistry of your tank
> changes (hardness in particular -- say a big piece of bogwood is slowly
> leaching tannins, or a calcerous sand is leaching carbonates), so does the
> conversion factor from pH to CO2 level.  So while you've still got a pH
> 6.82 tank, the actual dissolved CO2 might be slowly going up or down.  You
> have to do a re-calibration at each significant water change.  If I
> remember right, the pH probes also drift over time and have to be
> recalibrated in those special buffer solutions, right?
>
> There's also a hysteresis caveat.  Hysteresis = how long between the pH
> probe detecting the pH is too high & turning on the solenoid, and the
> injected CO2 dissolving and the probe reading low enough to turn it back
> off.  So if the needle valve is adjusted too low a rate, the controller
> will never shut off.  But too high a rate, then the controller won't shut
> off quickly enough and you get spikes.  And if the controller should fail
> on, the tank gets overdosed and kills all the fish.  So to do things
> right, you actually need to make the same basic adjustments on the needle
> valve that you do in a completely manual system.
>
> A good regulator/needle valve will be rock-solid for a lot longer than 4
> days.  It should keep up a constant rate for almost the life of the
> bottle.
>
>
> > I still like my idea though of filtering all your tanks fast enough and
> have
> > all the multi-tanks water end up in one place, then use a controller to
> > adjust as necessary. If that cycle repeast ast enough not sure why that
> > wouldnt be a great option, unless it comes down to cost which is
> typically
> > the #1 or 2 factor.
>
> Multi-tank means having a common sump to serve them all, plus lots of
> plumbing and overflows.  Overflows outgas CO2.  And common water supply
> means sharing disease and some algaes from tank to tank.  That said, I
> mention these problems because I have experienced them firsthand -- I
> have two aquariums attached to a common sump, and get common CO2 there.
> Plus water stability, algae and diseases.  :)
>
> And such a thing could very well work on an existing system like Jesse's
> (cf. 2009 Home show -- http://www.gsas.org/homeshow2009.torrent) where he
> has three cascading tanks on top of each other.
>
>   - Erik
>
> --
> Erik Olson                                                        Sent from
> my crusty old Linux box
> erik at thekrib dot com
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