Walmart offers the Aqua Fountain Aqua Cube 40-Oz. Pet Fountain, model no. PWW11-13591, for $17.97. Opt for in-store pickup to dodge the $4.97 shipping fee. That's $15 under the lowest total price we could find for this item shipped elsewhere. It features a replaceable charcoal filter, constant water circulation, submersible pump, and is dishwasher-safe.