for a small fish tank would be the Aqueon QuietFlow 10 Power Filter.

Quiet Aquarium Filters - aquariums pets fish | Ask MetaFilter
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The cheaper Quiet Flow Power Filter 10 is the smaller version of the Quiet Flow Filter 55/75, as is the QuietFlow 20, QuietFlow 30, and QuietFlow 40. The Power Filter 10 is meant to be used in small to medium fish tanks and can only process 100 gallons of water per hour. This freshwater aquarium filter includes all of the same features but produces on a smaller scale. Here are the stats associated with the rest of the Quietflow’s:
Quiet Filter Suggestions - Badman's Tropical Fish
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Most of you may not care for this filter but because of my small living space my peace and quiet is paramount. It is adequate for medium to small tanks in my opinion. And they work great for fish that do not like a strong water current. The downside to the filters is that they take up 'real estate' inside your tanks. But they really kept my tanks clear and were very quiet. Product - Ultra Quiet 3 In 1 Aquarium Purifier Fish Tank Aquarium Filter Built Filter ..
Photo provided by FlickrWhat are the quietest aquarium filters to use for a fish tank? - Quora
Photo provided by FlickrAqueon QuietFlow Power Filters and cartridges were designed with the fish and the aquarist in mind
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The Quiet Flow filter from is considered to be one of the best fish tank filters in the market right now. It is one of the most commonly used filters because of the features it has to offer and the affordable price. A nice characteristic of this filter is that it automatically starts up after the cleaning process or if there are any power interruptions. This is nice for someone who travels frequently because they do not have to worry about whether or not their aquarium habitat is remaining healthy during their absence.When the water is filtered out back into the tank, it comes out in the form of a waterfall that is both tranquil and quiet. The attached media basket prevents any water from by-passing the filter which ensures that every drop of water will pass through the filter. This is an awesome feature because it guarantees that the water in the fish tank will stay clean, clear, and healthy for the fish. For owners of a small aquarium, read up on our .Undergravel aquarium filters are another type of aquarium filter that you can use in a fish tank. The good news is that they are fairly quiet, but the down side is that they are fairly obsolete and I have talked to a lot of very experienced aquarium enthusiasts that cautioned against getting one because your are more likely to experience circulation issues. This means that some areas of the tank may get a good amount of filtration, while the other side of the tank may not get very good filtration at all. Overall, this means that it is not the most efficient route to take when choosing a quiet aquarium filter that does a good job of filtering out excess waste that causes high levels of ammonia and nitrate.: NEED HELP: What’s the Quietest filter on the market for smaller tank setups?? Maybe 10 gallon tanks. The sound of it needs to be silent. For college kids that want to bring their fish to their dorm room!The Penn Plax Cascade 1000 is a canister filter that is known for its high quality and sleek design. There is a button on the filter that can be easily pushed in order for the it to be primed or started. The rubber base on the filter ensures that it will stay in place inside the fish tank and prevents it from tipping over from the movement of the water. The extremely quiet flow rate is achieved by an airtight seal around the top and bottom of the filter.A great benefit of the Aqueon QuietFlow filters is the internal pump design that helps dampen noise, eliminates leaks and because it is self-priming, starts up automatically after cleaning or power interruptions. Higher flow rates also ensure a higher dissolved oxygen content for healthier, more active fish.