Another co2 ?

Hi all

A few weeks ago I ventured into plant keeping. They
seem to be just hanging on. Not really good, or very
Last week I made a co2, w/ a pepsi bottle. I put an
airstone on the end of the line. Plants seem to be 
doing a bit better. I'm also waiting for a couple of
new lights.
So, the question is, "can I put the tube {c02} down 
the uplift tube.??  I ask this cause I see people stick
the into powerheads.  It looks to me like it's losing
alot of the co2.
Thanks for any/all replies.