I'm upgrading my 20 gallon freshwater fishtank to a 72 gallon bowfront soon. My current filter is the kind that hangs on the side of the aquarium. It's not as noisy as the air pump, but it's noisy enough to bother Ed from time-to-time and I fear that a larger filter will be noisier, so I'm looking into my options:

Canister Filters:

• Look for an epoxy-sealed motor. From: http://www.aquariumfish.com/aquariumfish/detail.aspx?aid=9364&cid=3806&search=
• Magnet-drive motors are fairly reliable and convenient. They come with an on-off switch that may make priming the filter with water easier when getting it ready to run. Most canister filters with epoxy-sealed motors at the top of the filter require you to start a siphon to fill the filter. This may not be a very pleasant procedure for the aquarist. (from Aquariumfish.com)
• Magnet-drive motors require oiling and maintenance. Epoxy-sealed ones are maintenance-free.
• Magnet-drive motors are prone to failure if exposed to water, dust, humidity, etc
• “look for a self-cleaning impeller well design (or a slotted impeller well) that will ensure removal of slime and deposits from the impeller as it spins.” (from Aquariumfish.com)
• “The impeller should be covered by some type of plastic guard to protect it from foreign matter being trapped inside the well. Such material could jam the impeller and burn out the motor. As an added plus, the cover should have some type of seal or O-ring to ensure a positive seal.” (from Aquariumfish.com)
• “Make certain that the water either taken in at the bottom of the canister or is pulled down to the bottom of the canister so it can then be pulled up by the impeller through all of the media.” (from Aquariumfish.com)
• put “a small foam block on the intake to serve as a coarse debris screen”. From: http://www.wetwebmedia.com/ca/volume_2/cav2i1/canister_filters/Canister_filters.htm

Types of filters:

Canister Filter: It's like a bucket with an input and output tube that runs into the aquarium.

Pluses:

• “run a long time between cleanings” from: http://badmanstropicalfish.com/basics/basics_filtration.html
• “virtually silent” from: Badmanstropicalfish.com

Minuses:

• ?

Power Filter: This is like the one I have, it hangs off the back of the aquarium.

Pluses:

• easy to install and maintain

Minuses:

• ?

Undergravel Filter: Installed under the gravel, this filter provides biological filtration only!?!

Pluses:

• ?

Minuses:

• Biological Filtration only!?!

Wet/Dry Filters: “large open filter that sits under the tank and has sections for each of the types of filtration” (from: Badmanstropicalfish.com). This is the kind that we saw at Petsmart -it took up the whole back of the tank, but it was quiet…

Pluses:

• Provides all 3 types of filtration
• Usually has provisions to install a heater inside
• “Once set up the maintenance of these filters is easy.” (from: Badmanstropicalfish.com)

Minuses:

• “usually do not include all needed items, pumps etc.” (from: Badmanstropicalfish.com)
• can become a nitrate factory if not maintained properly

Submersible Filter: Installs inside the tank (under water)

Pluses:

• Silent(?)

Minuses:

• Difficult to clean
• Provides only mechanical filtration

Diatom Filters: Filters out particals small enough to be measured in microns.

Pluses:

• ?

Minuses:

• Not designed to be used all the time.

Interesting Links:

A rich person's guide to aquarium filteration: http://philip.greenspun.com/aquarium/filtration