Ok, CBBP....the pressure in the canister should be enough to expel the water from the tube. Effectively the tube is a syphon so water will flow up it.... (and, in certain cases, out on to the floor of your living room while you're in the kitchen making up the mixes! Amazing how much water can come out of a narrow tube in 5 minutes...... 5 big towels worth, i've found!

......keep the tube above the water level when not connected.....that's what i've learned!!)
Anyway, I digress....... I reckon your mix is wrong, probably due to using the rubbish ingredients that come with the kit... do a search on here for the co2 mix and redo... actually, hang on and i'll see if i can find it for you.......................
Here you go....
http
/www.fishforums.net/index.php?showtopic=139564