Emperor 400 noises

[jdllme]

I had an aquaclear 70 and had the same problem I took the inpeller totally apart and found out that the shaft had worn down due to sand

 

[KJP]

I like aquaclears too, but you have to somehow fasten the lid down so it doesn't rattle either!

 

[H20Boy]

I have the same filter and most likely sand found its way between the magnet and the shaft it spins on- this allows the propeller to dance around thus the noise--I would bit the bullet and pay the 16.00 @ the LFS replace it and the noise should stop.
Oh yeah you might have something growing inside you intake that is restricting the flow--by the way that is why the pump sounds up when you set the pump to it lower/lowest setting.
They are very reliable filters I have two no complaints--except the price of the filter cartridge!