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Re: CO2 problems

Hey, folks, we're forgetting some of the basics here. Adding CO2 to your 
aquarium is not like adding fish food - you need to think about what you are 
doing and exercise caution and common sense. Some aspects of CO2 are 
counter-intuitive, so a little uncommon-sense would be good, also. It wouldn't 
hurt to read a little about it before jumping in with both feet (check my web 
site). 

>But, you should be aware that adding CO2 to the water can and *will* 
>cause the pH to drop. Depending on how much CO2 is entering the tank vs 
>how much the plants can consume will determine your drop. 

The plants generally consume very little compared to how much is injected. A 
relatively large amount is injected to create a sufficient concentration to 
allow efficient uptake by the plants. The real determining factor in your pH 
drop is the carbonate hardness of your water. This is commonly known as KH and 
is usually measured with an alkalinity test.  If your water has low carbonate 
harndess (very soft), a little CO2 can change the pH drastically. You should 
determine your KH *before* you start adding CO2 and use the ubiquitous pH/KH/CO2 
tables to determine the proper parameters for your setup.  

>My 20 gal went 
>from a pretty steady 7.0 to down in the high 5s. I haven't checked my new 
>55 setup yet.

Gee, maybe it might be a good idea to check pH once in a while when you are 
injecting CO2!

>The main problem with DIY CO2 is it's uncontrollability. 

It's easily controlled, but the aquarist has to have some input into the 
process.  CO2 can be dangerous to your fish and you should be careful when using 
it.  Did I say that before?  

>Also, many systems can shut off the CO2 at night (well, when the 
>lights go out, anyway...), when the plants don't use CO2.

A pointless exercise. The CO2 used by the plants is small compared to the amount 
lost to the atmosphere when levels are in the 15 mg/l range.  You get far 
smaller pH swings if you leave the CO2 on all the time and control the flow 
properly. 

I wonder if any of the scientists among us have any info on how much CO2 plants 
use when they are strongly photosynthesizing?  I have evidence of how fast it 
diffuses into the atmosphere.   

George Booth in Ft. Collins, Colorado (booth at frii_com)
Need Info?  http://www.frii.com/~booth/AquaticConcepts.htm