I have a Sicce Xstream 8000 that I got used with my system and I noticed after purchasing a new 6500 that the 6500 moves way more water than the 8000. I put the 8k in a bucket to test it out and it flings water outward from the propeller but doesn't push water forward like it should. In the tank I saw food actually get sucked up into the front of the propeller and flung outwards. The only thing I can think of is that maybe the propeller is the wrong one since it was used I have no way of verifying this. Or maybe there is a spacer that I am missing that keeps the propeller out away from the housing? It seems that this propeller is closer to the housing than the others. Anyone ever have this issue? Oh and it is spinning the correct direction.