What have you tried?

The quietest filter for that size tank is going to be one of the in tank power filters like a fluval 1 or a duetto shark. These filters are ok, not great, but ok. Just be careful not to change the foam in them. Clean them during a water change by rinsing and squeezing them in the used tank water (NOT fresh tap water, the chlorine will kill the biological filter). The one drawback of these is the filter material is pretty small and in one piece, so if you actually change it with something new you've removed your biological filter. Better to just clean out the sponge.

If you went with one of these I'd also stuff as many plants in there as possible *if* you have the light for them. Good low light choices are anubias, java moss, and java fern. These are all pretty common and can survive in lower light levels (although more light would help a lot). It is very feasible to have a tank this size where plants are the only filter, but if you haven't done this before it will be a new challenge for you. If you wanted to go this route do a web search for "Diana Walstead". She wrote a great book called Ecology of the Planted Aquarium. Its very technical, but the practical side of it is reasonably easy and you should be able to get a lot of info on the web.

Sorry, the correct spelling is "Diana Walstad".

I would use the small power filter from walmart the only problem is if the water gets low it will sound like a brook until you fill it. I find it a relaxing sound. The filter pads are easy to change and like air conditioner filters work better the longer you leave them alone. and you can rinse them out a number of times. I use the sprayer in my sink the bacteria will reastablish from the tank. Remember clenliness is next to Godliness doasn't apply to fish tanks I have a Twenty ,A twentynine ,a forty and a one hundred twenty five and don't use air pumps on any of them and they're all overcrowded with fish also more fish are killed from over care than letting things get dirty. If you have Questions email me at phal677@yahoo.com . I dont often check the postings on this page these people make to much work out of a common sense hobby

It depends what is generating the noise. The equiptment? Or the surface agitation from the equiptment? Either way a few tips.1) Get a glass canopy/hood instead of plastic hood and light combo ( assuming thats what you have). Place your light directly on the glass. This will work somewhat like closeing a window when there is a noise outside. Other benefits are less evaporation of water and it helps retain heat in winter months ( the opposite in summer, if it gets the water too warm prop the top a little to let warm air escape). 2)Raise the level of water to reduce surface agitation from filter cascades or bubbles from the airpump.3)Put the airpump on a sponge or cushion the bottom of the pump (careful not to cover any vents)with self stick felt or both. 4) If using a hang on back filter cushion the part that has contact with the outside of the tank. 5)Clean the impeller of the filter when doing routine maintainance they sometimes get gunked up and cause a vibration .6) Another option is use a submersible pump/powerhead with a sponge over the intake.

I use a Rena air pump. very very quiet. Can't hear anything at all.

What about the Whipser filters, I find mine to be very quiet, I can't hear it at all and I have super sonic ears too! I have mine on a 29 gallon tank at home but where I used to work, they had one on a 10 gallon tank and we couldn't hear it at all. That's the main reason why I got one for my 29 gallon tank.

yes please try a whipser filter my husband got me a 29 gallon fish tank for christmas a few years back and the filter it came with was very loud . and my husband couldn't stand the noise .so he went to wal-mart and got a whipser and it has been one of the quietest filter i've got .