Keeping live plants in an aquarium happy can be quite a chore. One of the frequent rituals is adding fertilizer, which is called dosing. [Majstor76] came up with a creative way to automatically dose using an air freshener. He got rid of the canister that holds the scent and re-purposed a hand soap pump to move the nutrient-rich liquid. After the break you can see that there’s no shortage of power to actuate the pump and the powered air freshener base has a delay circuit, allowing for a few different time-release options. As long as the volumetric output is fairly consistent we figure you can dilute your fertilizer to fine-tune the dose.