Recently upgraded my air pump to the Eheim Air Pump 200, with dual output. My previous air pump was not strong enough to power 2 sponge filters simultaneously.
This Eheim Air Pump is very strong. In fact, it is almost too strong, I had to lower to the lowest setting for my 2 gallon nano tank. For the 5 gallon tank, I select the medium setting, and angle the output towards the wall. The sponge filter output was made to be above the water level (there is less turbulence this way).
Overall, this air pump is very good and quiet. Do expect some noise though, it is not totally silent. I would say it has the same noise level as a fan, which is totally acceptable. Also, I find that the 2 adjustable valves are not totally independent, when I adjust one valve it will affect the other output as well.
Review: The Eheim Air Pump is a highly recommended air pump for fish keepers with 2 aquariums.
The Eheim 200 Air Pump is also labelled as Eheim PHL207184. There is a more powerful Eheim 400 (twice the output), but based on my review most aquariums under 50 gallons should not require such a powerful pump (maybe 50 gallons and above may need it).