Re: C02 problems

    In my wife's 20 long plant tank we use diy CO2 with yeast,
sugar, baking soda, etc., in the 3 liter soda bottles they favor
here (it is Texas, after all:). The airtube runs into the air intake
on a sponged powerhead, providing dispersal and an easy 
means of gauging each bottle's status (we get about 4 weeks
from each). Clogging is unlikely since we don't use an airstone.
To prevent pH shock, (because her tank has a blue craw and
small fish), we run a tiny air pump through a wooden airstone.
This removes some, but not all C02 (here in TX the tapwater
runs 8.1 or .2 after aeration and could buffer battery acid). So
pH with injection is 7.2 to 7.4. The air pump also assures
that fish don't suffocate after lights out.

    So far this system has worked well in two 20 gallon tanks
for the past six months. The only thing I haven't done is placed
valves on the CO2 lines to prevent siphoning. Unless I'm
greatly mistaken, siphoning in the instance of powerhead
failure and insufficient gas pressure in the bottle would fill
it all the way, about one liter, then stop because the bottles
are well sealed. 

Andy Katz