Newbie CO2 help needed!

Hi there.

I have a 40G tank which I have recently planted up. I have got a Hagen Plant Grow CO2 system (http://www.petsmart.com/product/index.jsp?productId=2754083), but the bubble ladder has broken so I am looking for other ways to diffuse the CO2. I have got the canister/reactor under the tank, with in line valves in the tubing up to the water level. This is then fed into the canister of a very small internal canister filter, a very early Fluval 1 that my dad has had since the 90's! I have checked 'youtube' and most I looked at seemed to have the filter at an angle to "spin"(?) the CO2 in the canister before it goes up into the powerhead, theoretically diffusing the CO2 into the water.

The problem I seem to be having is that it isnt working! I dont seem to be getting any CO2 up the line into the canister. The yeast mix was the same as normal and I checked it was still in date, so it should be working. Can anyone shed some light on any reason you might know why its not working? Its been 5 days now and still no bubbles! Could the in line valve be too strong for the gas to pass?

One last question, is there a certain amount of CO2/BPM that is optimal? Or does it depend on the tank size etc? If there is an optimal amount, does it need to be going for a certain amount of time per day/shut off overnight?

Any help will be appreciated. Thanks in advance.

Hopefully get a pic of the tank up here to start "tracking"