Hagen for a 30 gallon is pushing the limit.
Give it some time, use the mix posted above, then if you are still unhappy, try using a larger canister, a soda or juice bottle (juice bottle is square on bottom and more stable). You will lose the benefit of having the bottle hung on the tank, but you may be albe to rig up some sort of holder to keep the bottle level with the tank -- this eliminates the possiblilty of siphoning, which can easily happen with the bottle under the tank.
Oh, with the Eclipse hood, does that have a biowheel? Or does it cascade water into the tank? That fallling water can drive off the CO2 you are adding. So, take a look at surface disturbances and how that affects the CO2 you lose.