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Re: Air Stones vs Plants vs CO2

On Mon, 30 Sep 1996 15:39:04 -0400, Aquatic-Plants-Owner at actwin_com wrote:

>Of course aration will decrease the effectiveness of CO2 injection. That 
>doesnt make aeration bad for plants however. My point was that CO2 
>injection is unnecessary under most conditions and that the same effect 
>could be achieved through adequate water movement in the tank. Why? 
>because limitation of growth by CO2 is not due to the inability of plants 
>to fix CO2 but rather due to the high diffusive resistance of CO2 in 
>water. To increase the rate of diffusion you can increase the gradient 
>(CO2 injection) OR decrease the path length (water movement, aeration 
>etc) ... which is easier? CO2 injection is only necessary when you are 
>growing plants which are completely unable to utilize bicarbonate AND are 
>exposed to elevated CO2 in their natural habitats ... such as matt 
>forming species which trap CO2 that has been release from the sediment.

Just how much water movement are we taking about?  How many gallons/liters
per hour say for a 150L (40gal) tank?  Would a more turblent flow decrease
the flow needed?  ie. some sort of 'wave' box.  Sound like an interesting
experiement...

>The whole hearted endorsement of CO2 injection is part of what I call the 
>'sick and dying plant' syndrome ... people have this opinion that aquatic 
>plants are delicate and hard to grow and so treat them like a dying 
>patient hooked up to life support. In reality, however, most aquatic 
>plants are agressive, noxious weeds and will readily take over your tank 
>given even half a chance. For example, a few years ago I was charged with 
>the task of growing large quantities of healthy Lemna trisulca (the 
>submerged duckweed). The experts said it was very difficult and that you 
>needed a sugar supplement and a full complement of vitamins and very low 
>light (otherwise the plants would die) and an acidic pH etc etc. Yes, I 
>grew Lemna trisulca under these condition but it was difficult and 
>incredibly time consuming. Then I thought, this is crazy, and I removed 
>the sugar, removed the vitamins, increased the light to about 20% full 
>sunlight and incresed the pH to 8.0. The growth rate more than DOUBLED! 
>the plants were healthy, and I spent my time doing other things rather than 
>carefully nursing 'sick and dying plants'.

This is interesting.  I follow the PMDD regime except for the CO2.  Each
tank get about 2 turn overs per hour.  Would tend to disagree with the
reason you supply for CO2 usage - CO2 often lets plants grow like weeds.
Often this is the desired effect.  It would be interesting to try a CO2
setup with slow flowing water and one with fast along with two other
tanks with slow and fast flow without CO2.  


Ed Tomlinson (tomlins at cam_org)
Montreal, Canada

Home of pppdial: http://www.cam.org/~tomlins/pppdial.html