I haven't measured CO2 ppm, but my vals, hygrophila, and java fern really took off when I started the CO2 by having it pull into the inlet side of my Magnum 350 canister. This seems to work well, as the CO2 bubbles follow a vigorous flow of water into the canister, through the pleated filter, then through the impeller and exiting up the outflow pipe and tubing back into the aquarium where it is deposited a couple inches under the surface via the standard Marineland outflow device.
It's all completely dissolved by the time it gets back into the tank, and mine's an even 100 gallons. I only use medium gravel and another Magnum 350 pulling through 4 UGF plates.
v/r, N-A
