You can try googling "wet/dry filters" as well.
Basically, the water overflows the plastic part of the tank and drains, through a tube, into a box below the tank. The water then "trickles" through filtration media with a lot of surface area to grow beneficial bacteria and also to mechanically filter out the bigger waste. The water then flows into another compartment that then pumps the water back up into the tank.
I have one on my 90g african cichlid tank (mbuna). Maintenance consists of cleaning off the pad in the top of the filter, where the water dumps. You can also rinse off the bio balls (or scrubber pads or whatever you use for the bacteria) periodically, but only a part at a time to maintain the bacteria. If you rinse it all at the same time, your tank will have to cycle again.
If none of this makes sense, look up "wet/dry filters".
