quietest filter

A Rena XP2 is what I would put on there. I have three XP3s on my larger tanks and you have to put your ear physically on them to even tell they're on.

Is your tank getting a lot of direct sunlight? You must be getting a ton of evaporation to even be able to top it off every day.
 
I have tried most of the filters listed on here and I have found that the AquaEl Unimax is the absolutely most quiet filter I have ever run. I have to feel the filter to make sure it is running to feel a slight vibration from the motor compartment. I have never heard anything so quiet.

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=12702
 
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