BioCube filter.. ?

[bsmith]

I just bought a 29gallon Bio Cube set-up. I like it a lot, it comes with about everything. I went to set it up and I put the sand and water in and turned it on but the side has a vertical level of where the water should be in the pump compartment. well i cant get the water level to stay in the middle area. it keeps going low and the pump shoots air and water out into the tank. I let up the filter in another compartment to allow more water to flow and it worked, but as soon as i put it back the water level would go back down ! Is there any harm to letting the filter stand out a little? Also there is a middle compartment with bio balls and i "hood" that the water goes over to drip over the balls and if i took that off, with the filter all the way in properly, the water level went up in the pump compartment.. any way to prop that up so it allows more water to flow faster over the balls?
any help please !
thanks