Re: DIY CO2 injection

>I have already leart that DIY CO2 injection can be made from 2L soda
>bottles and that the mix should be 2 cups of sugar, 1 tsp of baking
>soda and 1 tsp of yeast. I understand the bottle should be filled
>almost to the top with watter then.

Six cups of water is enough. Don't fill it to the top because the yeast
needs room to foam a little.

>Besides the composition of the mix,
>does the temperature matter much?

Warmer water in the yeast bottle will make the yeast reproduce more quickly
and produce more CO2. The yeast will also not live as long when it's warm
because its metabolism has speeded up.

> And, is it possible
>to kill the fish by injecting too much CO2 - either by making the
>carbon dioxide replace oxygen in watter of by making the Ph drop too
>much? If so, how can I controll how much CO2 is injected with this
>setup? Finally, I understand the CO2 will make the Ph drop. Should I
>counter this by adding some baking soda to the tank watter?

You've got to accept that you're not going to have precise control over the
rate of CO2 injection with a simple DIY yeast concoction. That's why the
high-tech folks talk about regulators, needle valves, bubble counters, etc.

But you needn't worry too much about it either. The hardness of your water
will put a lower limit on the pH drop. Just watch your tank water carefully
after you've set up your CO2 system. Once the pH stops dropping, that's the
pH you'll have until you run out of CO2. (Ideally, you'd observe the pH
effect while your tank doesn't have any fish in it.)

If the pH drop is too much, then you can think about buffering your water.

Greg. Tong
San Francisco, CA, USA
gtong at sirius_com

"Every infinity is composed of only two halves."