The Tetra Whisper In-tank Filter 3i, assembled and ready for use.

The Tetra Whisper In-tank Filter 3i for 1 to 3 Gallon Aquariums

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By: Jean Flint

The Tetra Whisper In-tank Filter 3i, assembled and ready for use.
Small, easy to put together.

A year ago, I was letting my betta fish swim around in unfiltered water that I changed once a week. Not ideal, I know, but within acceptable standards of habitat maintenance. Then I found the Tetra Whisper In-tank Filter 3i at my local pet store, and decided to buy it based on its small size, affordable price, and suitability for delicate fish.

The Whisper In-Tank Filter is designed to handle up to three gallons of water, and at 2.5 inches wide by 1.75 inches deep by 4 inches high (plus the extra inch above the bottom of the tank at which it should be placed) should fit handily into most small aquariums. It filters up to 20 gallons per hour and creates a gentle current that my fish doesn’t mind at all.

Packaging includes a filter, air pump (115V 60Hz 1.2-watts), package of two small Whisper Bio-Bag Disposable Filter Cartridges (also available sold separately), two feet of air line tubing that are easy to assemble into a working tank filter, and a limited one year warrantee.

Its suction cups make it easy to attach to any flat-walled tank and easy to adjust the height of the filter if the water level changes. I found that it has improved the quality of the water and made the tank easier to clean, as any filter might, with the added bonus of being easy to clean itself. Even the suction cups can be removed and cleaned individually with a brush. The cartridges are very simple to replace.

The name “Whisper” is a bit misleading. The air pump vibrates, especially when placed on a hard surface, so I keep a folded-up washcloth underneath it to muffle the sound and to keep it from moving around. Others place it on carpeted areas as the two-foot air tube allows. That keeps it quiet, though still not quite the “strong silent type” as claimed on the box.

Fair warning: the air pump can wear out with constant use. I had to replace mine after having it for several months. The simplest way to replace the pump is to buy a whole new Whisper In-tank filter, because the air pump is not sold separately. Other options for a small aquarium include the Top Fin Air Pump AIR-1000 and the Rena Air 50, which can attached to the filter with air line tubing just as with the original air pump.

A home aquarium with a Whisper In-tank Filter and a male veil-tail betta.
The Whisper In-tank Filter keeps this male veil-tail's water nice and clean.

This is a good filter for my betta in his 2.5 gallon tank, but keep in mind that he usually stays pretty close to the surface of the water, away from the bottom of the filter where the suction is strongest. The Whisper In-Tank Filter might not be ideal for fish, particularly slow-moving ones, that spend more time at the bottom of the tank, because there is no way to adjust the amount of suction.

For tanks larger than three gallons, try the Tetra Whisper Internal Power Filter 10i (for up to 10 gallons) or the Tetra Whisper Internal Power Filter 20i (for up to 20 or 40 gallons depending on desired gallons per hour), which have quieter, internal motors.

As far as keeping the water in a small aquarium goes, the Tetra Whisper In-tank Filter 3i is an easy-to-use choice. I recommend it particularly for use in a tank with an easy-to-keep fish such as a betta.

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  1. i use this for my 1.5 guppy tank. the filter filters the water but doesnt make bubbles at the top. is it still providing oxygen? is there anything i can do to fix this? thanks

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    1. Actually it is oxygenating the water as it is moving it through the filter. It does not, however, provide bacterial filtration which is very important. without it you have a tank that has to recycle every time you change the filter. I would suggesting adding a small piece of sponge or a couple of pieces of bio media to the filter to provide bacterial colonies that will not be thrown away when the cartridge is replaced. I assume you have no more than three guppies in such a small tank, with no other livestock, and are using a heater.

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