Re: CO2 rates and biowheels

[Dave Millman <dave at tactics_com>]

At 12:48 AM 5/9/02, Diane Brown wrote:

>The CO2 is up and running (thanks, Dave).  Dave suggests an initial CO2
>injection rate of about 1 bubble per second per 50 gallons of tank volume.
>Can any of you who use a similar system with Eclipse hoods and biowheels
>suggest by how much I should anticipate increasing that to compensate for
>the CO2 blown off by the biowheel?

Diane,

Don't worry about the biowheel. The CO2 lost just means you will need to 
inject a bit more to get the same dissolved concentration, all other things 
being equal.

Here's what to do:

1. Start with Dave's recommended rate above.

2. Wait 4 hours and measure pH & KH.

3. Refer to a CO2 chart to get your dissolved CO2. My favorite is
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

4. Adjust your bubble rate to raise/lower the CO2 as desired, and repeat 
from step 2.

Caveats:

A. Understand that KH drops slowly over time, in between water changes. If 
your KH is 3 or greater, you don't need to measure KH too often. If it is 
lower, measure KH every couple of days so that you understand how quickly 
it drops between water changes. Since added CO2 lowers pH, you want to 
avoid an unintentional pH crash caused by your KH dropping too low (below 1 
or so).

B. Once you have achieved the CO2 concentration you want, check your bubble 
rate every day until you understand how it changes over time. Different CO2 
setups are more or less stable depending on component quality, room 
temperature, tank pressure, regulator settings and who-knows-what.

C. Keep in mind that, at a constant bubble rate, pH will tend to drop 
during the day as plants consume CO2, then rise at night. If you are a 
stickler for accuracy, replace step 2 above with "Measure pH at the end of 
the light cycle the next day."