[APD] Re: Tiny bubbles or keeping the nutrients higher than needed

["Michi Henning" <michi at zeroc_com>]

> Message: 6
> From: Thomas  Barr <tcbiii at earthlink_net>
> Subject: [APD] Re: Tiny bubbles or keeping the nutrients higher than
needed
>
> "Tom gives a compelling argument for using a fixed CO2 bubble rate
> (without pH controller) in message
> <http://fins.actwin.com/aquatic-plants/month.200201/msg00209.html> Once
> you have established the steady state CO2 for a given pH and KH, you can
> then keep that CO2 injection rate constant and ignore pH and KH from
> that point on!!!"

Personally, I use a pH controller for a number of reasons:

- I'm shooting for 20-30ppm and, depending on whose advice you believe,
  somewhere not too far above 30ppm, CO2 toxicity becomes an issue. I'd
  rather not wake up to tank full of dying or dead fish one morning just
because
  the bubble rate wasn't quite right.

- The tank isn't static -- I do water changes, I prune, I add nutrients, and
I don't
  necessarily do all these things like clockwork at fixed intervals. Those
changes
  affect plant growth and biomass, and are likely to affect CO2 uptake.

- The KH of my town water supply isn't stable -- it varies between 4.5
degrees
  and 6 degrees. That difference is significant in terms of the amount of
CO2
  that is dissolved in the water at a given pH.

- I find that getting a truly consistent bubble rate out of my needle valve
is difficult.
  The bubble rate varies with ambient temperature and, as the tank gets
toward
  empty, with the amount of CO2 remaining in the tank.

So, I see advantages to using a controller. For one thing, I don't need to
worry
about precisely controlling the bubble rate. Instead, I can just let the CO2
run
at quite a high rate, say 5-10 bubbles per second, and rely on the
controller
to switch it on and off as needed. Also, the pH controller gives me a very
precise
reading of the pH (+- 0.01 degrees), and I can measure KH quite precisely
(down to +- 0.25 degrees), so I know where the CO2 level is to within quite
a small margin of error.

I don't think that a controller is essential by any means. I know many
people
who successfully use CO2 without bothering with a controller. But it's nice
to have one. A bit like a cruise control on a car -- convenient, not
essential.

Cheers,

Michi.

--
Michi Henning              Ph: +61 4 1118-2700
ZeroC, Inc.                http://www.zeroc.com


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