snip
The only time I ever had a leak from the 2 liter bottles was when it
was knocked over on it's side... the pressure from the CO2 forced the
fluid up into tank... fortunately I caught it before I lost too much
fluid... of course, it was a mess to clean up... i had to force bleach
through the tubing, bubble counter etc then flush it very well with
clear water and start the whole system back up again. I lost about
1/4 cup total fluid up into my tubing etc, so less than that actually
made it into the tank.. fish etc survived well, but I made a 30% water
change that day and the following day just to be safe.

I have seen someone advertising acrylic racks for holding 2 2 liter
bottles on aquabid... that will probably be my next purchase, 3 or 4
of those should suffice for my current setups...

I have experienced the same problem with 2 liter pop bottles falling over. The
problem is the bottom is not a very stable surface. To solve this, I switched
to 1/2 gal plastic juice bottles. They have a flat bottom that doesn't tip
easily and they are made of a much more sturdy plastic. And fruit juice is
better for you than pop, didn't your mom ever teach you this?
Nick Wise

Hmmm.... yeah but... I like my rum-n-cokes! Of course, I guess I
could change that to something more fruity and use juice instead!