Have a DHT11 as an input, watering frequency based on humidity or temperature. For instance, a higher temperature results in more frequent watering.
Initally, I planned to 3D print my tank but due to it not being economically viable due to the large size, I would instead laser cut my water tank from acrylic, sort of like a fish tank.
An arduino project involving an all in one sensor, uses serial monitor to output data.