The small Eheim PickUp is ideal for small aquariums. The filter is attached to the aquarium with suction cups. The special thing about the PickUp is that the motor remains in the aquarium when the filter holder with the filter sponges are removed.
The bottom of the motor sucks in the water and pumps it through the filter sponges. The cleaned water is then pumped back into the aquarium through the adjustable outflow nozzle.