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peat or soil as DIC (CO2) substitute
DIC (dissolved inorganic carbon) refers to the amount of dissolved CO2
in the aquarium water and is very important for maintaining pH control
and good growth in a well lit and otherwise fertile aquarium with
It seems almost a given that we will recommend either compressed CO2
from a cylinder or the yeast-sugar method for generating CO2. Some
folks infrequently mention the "low-tech" method which commonly uses
much lower lighting levels (.7-1.5 w/g), some type of peat or soil
substrate and minimal chemical intervention. It is reasonable to
suspect that much of the CO2 requirements are being met by the action
of decomposition bacteria acting on the organic material of the
Many types of aquatic plants have evolved specialized methods for
obtaining carbon or CO2 requirements from carbonates dissolved in the
water of their natural habitats. In an aquarium without CO2 injection
(or an alternative source) these plants employ a method called
"biogenic decalcification". It is called this because the removal of
carbonate ions from solution causes the precipitation of calcium which
can be seen as white deposits. This is also accompanied by a rapid
increase in pH, in some cases as high as pH 9 to 10 by certain plants
like Elodea, Egeria and Saggitaria.
Since I often keep small fish like killies in many small tanks and I
prefer to use plants in those tanks to supply oxygen and consume toxic
wastes, I often use peat along with Elodea to maintain a stable pH.
It's simply not practicle to perform CO2 injection on these small
tanks. Tanks with Elodea and no peat will rapidly get high pH and
become unsuitable for fish or other aquatic organisms. Those with peat
have an extremely stable pH of about 6.7 or so. I expect that soil
with some amount of organic matter will also exhibit similar
I have some questions:
Are the products of the biogenic decalcification (or the agents which
are responsible for that chemical acitivity) actually liberating CO2
from the organic acids or organic materials from the peat?
Can aquatic plants meet carbon or CO2 requirements from peat?
Could a larger system with stronger light and growth requirements gain
sufficient DIC using only peat or similar materials without CO2
injection to maintain a reasonable pH equilibrium? My suspicion is
that this is unlikely but I'm curious if anyone has tried.
To suggest that peat or dissolved organic carbon (DOC) should be used
in place of CO2 injection is not something I (or most here) would
recommend at this time. Peat and other organic soil materials tend to
liberate large amounts of nutrients such as nitrates and phosphates.
This can produce very rapid growth of plants but can also cause severe
algae problems. Organic acids also interfere with the chemical systems
used to measure CO2 content or hardness.
A little plug for The Aquatic Gardener magazine published by AGA: I
have a fairly lengthy article there discussing peat and other
substrate materials in a forthcoming issue.
Steve Pushak in Vancouver (after 2 mon vacation in Philippines)
more on Philippine plants and fish later...