DIY CO2 Setup Question

[torch89]

I want to add a DIY CO2 system out of a single 2L pop/juice bottle.  The DIY project I was reading about suggests running the tubing into the intake valve of the power filter.  Claims with one bottle, will do a 20-30 gallon tank.  Planning on using it in my 20 gallon tank, with 55 watts of light (all bulbs 6500k and high color rendering index), with Flourite substrate.  My questions is, is this safe?  How would I know if it was supplying too much C02, or is such a small system something I shouldn't worry about?  Don't really want to kill any fish because I try adding C02.
Thanks for any input.

[BigDaddy]

What makes it unsafe is if you mix too much yeast to sugar and produce too much CO2 at once.

The standard receipes are anywhere from 1/4 tsp to 1 tsp of yeast to 2 cups of sugar in a 2L solution.  How much CO2 you get will depend largely on how effecient your reactor is (a power filter is marginally effecient, but there are better options).

Do it on a weekend when you can measure the pH regularly and can keep an eye on the fish for signs of distress (gasping at the surface... generally "lazy looking" etc...)

You'd really have to screw up your receipe pretty badly to overdose a 20 gallon using a power filter though...

[torch89]

Thank you Big Daddy for your quick response.  Now, I'll just have to give it a try and monitor.

[Adam]

I have 3 2L bottles on my 14 gallon...the pH dropped a little, but my fish are all fine.  It's been almost 2 months and it hasn't quit bubbling.  I used 1.7 tsp, 6 cups of sugar, and 1.5 tsp of baking soda...distributed between them.  The water goes up to the neck of the bottle.

Adam