co2 sup via water supply?

Im no biologist but I see a lot of growers "filling rooms" with co2 systems on timers.

I grow in a DWC and was wondering if its possible to use an aquarium co2 unit like either of two below to "feed" the plants via the root system.

1: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=290269685235

2: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=120384157748

If I am not mistaken plants breath from both roots and leafs. It seems it would be easier to fill a small 5 gal bucket with co2 then an entire closet.

Just a thought, looking for some experienced incite.

I would be very interested to see that. I've been wondering how I can do a cheap co2 system that would work. I'm kind of iffy about the other DIY C02 systems but may have to settle with them.