Co2 Dissolving in Water

OK, another topic on Co2.

So, I have 2, 3-liter bottles cooking up the good ole yeast fermenting
sugar.

I have both connected to a T-connector and then the line goes into a
plastic, rectangular bell container that comes with Jungle's Co2 Fizz
Factory.

The instructions on the Fizz Factory says to submerge the bell container
just below the level of the water. However, I got to thinking, that by
possibly putting it further down in the water, say a few inches from the
bottom, that the water pressure would be greater and cause the Co2 to
dissolve quicker.

But, it doesn't appear to be working. Both the 3-liter bottles are on their
last leg and need to be energized, but I am only getting about one bubble
per 10 seconds into the bell container. When I empty the bell container
from all built-up Co2, the next day the bell container is almost full again,
like it is not dissolving into the water.

So, what do you all think? Would it be best to put the holding unit just
below the water level, or further down in the tank?

My plants have been 'sleeping' lately and haven't been growing at all, but,
that could also be due to the fact I changed from gravel to sand recently
too.

Brian S.