Tetra Whisper Air Pump (Non-UL) by Tetra.

Of course this is intended for use with an aquarium.  Homebrewers use similar pumps to aerate wort.  Aeration can help reduce lag times, encourage yeast cell reproduction and produce more vigorous fermentations.

Typically you would use both an aeration stone and an inline filter along with this.

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Tetra Whisper Air Pump (Non-UL)

Also Consider: Oxygenation Partial System FE376  from MoreBeer | Yeast Starters & Fermentation Resource Page · StirStarter Stir Plate | Carbonating Stone with 1/4″ Barb, 0.5 micron | Sanitary Filter

More: Recent Amazon Finds

Oxygenation and Aeration Supplies at William’s Brewing