these are 2 10 gallon tanks that sit right next to each other.
they both share the same 30 watt power glo bulb.
both tanks use play sand as a substrate.
neither tank gets ferts.
the tank on the left gets co2 via a ceramic diffusor. its placed in the front corner of the tank, not in the flow of the filter.
the tank on the right gets no co2.
the only difference between the two tanks, is that the one on the left gets co2.
they are both planted with aromatica, and planted at the same time. the growth in the co2 tank has far eclipsed the non co2 tank. in the same time period, the co2 tank has been trimmed down 1 time to half its height and subsequently grown back to what you see now.
there is no implication in regards to the ferts.
the fact that there is no ferts is mentioned to keep the focus on just co2 and not have another variable that growth can be attributed to.
this photo comparison illustrates the importance of co2 and what kind of difference it can make just in itself.
If you had dosed ferts the difference in growth would have been even more dramatic since carbon would have remained the limiting factor in the one tank while nutrients would not have been a limiting factor holding the Co2 tank from utilizing even more carbon.
The fact that there were no ferts used and yet the differences between the two were still so dramatic says a lot for what a fertilized, well lit, carbon enriched tank can do that a tank with a limiting factor just can't compete with.
picture example of c02 vs non c02 tanks 
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