Help with Aqua Tech 5-15 Filter?

I have had one of these filters before and I remember them working well. We just bought a new one and it sounds like it is sucking up water but nothing is coming out. We only have our 10 gallon tank filled about a 5th of the way because we are going to breed my betas. The whole end of the sucker tube is submerged. We have read the directions and just can't figure this out. We have also tried adding water to the reservoir and it just overflows and nothing more happens.