New Fish Tank Help ?

My mom and I just bought a new fish tank from Pet Land Discount. We bought the combo. There is something call an Elite 799 Air Pump. I read the instructions and put the tube part in the container connected it to the pump it started blowing air so I put it in the tank. (I hold water and gravel in the tank already). The problem very soon is that there is something caled a bottom filter. It looks squarish it has a long tube aand a plate in the bottom. As soon as I put it surrounded by the water it started bubbling. There is no instructions for it. I put it in the corner and it keep moving.
Answers:    i had something like this its a cheap excuse for a "filter" the filter didnt work for me and my fish died so before u make the addition of fish u may wanna get a new real filter
that's the course it works there should be a way of holding it down
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