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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...