as another note:
i currently run the emperor filters, and am really stuck between them and the aquaclears.
emperors: very well made, can be a bit "gurgly" , flow control does NOT work as intended, bio-wheels are good, bags are EXPENSIVE!!- but you can make your own...
aquaclears: overall construction is weaker than the emperors, cheaper than emperors, not as noisy as the emperors, but lids can rattle sometimes without weight on top, filter holds A LOT more media, flow control actually works, etc etc.
to me they are both great filters-- if you like to be able to buy media and just keeping rinsing and re-using go for the aquaclears, b/c the sponges last almost forever.
either way you will be in good shape.
the penguins are also good filters, but i hate how the bags clog so quickly!! after a few days the water is running 50% over the intake pipe it seems like!
M