I have a used Marineland Emperor 280 and I tested it today, it seems to do the opposite of its intention, instead of filtering water through and back into the tank it is somehow draining itself of it's own water? If I fill it all the way it comes out the spray bar for a while but not the lip and you can see the water level dropping, after a few seconds it doesn't come out anywhere at all but the water level continues to drop, what is happening?