Join Date: Jan 2004
Location: Las Vegas , Nevada
The water in the tube should start at the water level and then slowly move downward as the pressure inside the canister build up. If nothing happen in 20-30minutes and you mixture is active, there is a leak somewhere. It doesn't mean that your mixture doesn't produce CO2, it just doesn't create enough pressure because of the leak. To check whether your mixture is working, you can use a flashlight pointing to the surface. You should be able to see a lot of micro bubbles moving to the surface. They are extremely small and look more like white dust moving up.
I read a question that someone posted at the Hagen website. He was asking whether it is safe to connect the DIY CO2 output to the venturi. The technician said that there is no definite answer. The design of powerhead did not take into account that function. He said it all depend on how powerful the powerhead is. If it's too powerful, the suction on the venturi can collapse the bottle.
Why don't you just stick the output tube to the filter intake. It'll have much less suction there.
Also, try to apply some silicone sealer to all connector to make sure there is no leak there (it happened to me twice, once at the T-con. and other at the tube connector). Those silicone is easy to peel if you want to disconnect it one day.
It took me all night long to figure out those leaks (and another all nighter the following week), so don't give up yet.