CO2 Problems Re: Aquatic Plants Digest V1 #188

> From: "David Huie" <David.Huie at Bentley_COM>
> I have a problem that I'm hoping someone can give me suggestions on.
> The first time, the tank just ran out and the pH went from 6.2 to 7.8 
> in about two hours.

Does your regulator have high and low pressure gauges on it?  If not,
and you can't tell when the tank is about empty, this is going to be
hard to avoid. 

You can ameliorate the situation by careful control of the buffering
and amount of CO2 you are injecting.  Based on the pH range you
mentioned, you either have very low buffering or high CO2 or both.  
Perhaps you might want to keep your pH at 6.8 to 7.0.  Plants do well
there.  If you want a low pH for fish, I don't think CO2 is the way to
get it.

We maintain a pH of 6.8 in our discus tank with 15 ppm of CO2, which
is plenty for the plants.  If the CO2 quits (which can happen even
with pricey controllers), the pH will go to 7.8.  An occasional
excursion like this doesn't seem to harm the discus.
> The second time, last week the whole CO2 tank vented into the aquarium 
> at once--a one inch shell of ice on the CO2 canister was a bit 
> bizarre.

Any idea of this happened?  I would think the regulator should prevent
a CO2 release this quickly.  Do you have a fine control valve after
the regulator?  In a manual setup, you really need a good valve to
control the flow to 1-2 bubbles per second.  A proper setup should not
have very high pressure on the aquarium side of things; just enough
to force CO2 through whatever injection device you have.  

> Isn't there a reasonably affordable reaction chamber available to help
> dissolve CO2?

Whatever you find, you still need good control of the CO2 flow.  That
should be your first priority.  Most folks I know have had good
success with almost any kind of reactor as long as they could control
the flow.  A decent fine control valve should run $10-35.