One bulky part of every automatic irrigation or hydroponics system is a reservoir for the nutritional water solution. Depending on the setup requirements, you will find the right size for your plantation.
Mind, that depending whether drip to feed or drip to waste setup is in use, you might need one additional reservoir for used water. In the traditional hydroponics, however, there is just one single nutrient vat, from which all feeding proceeds.
Though they work well with each other most of the time, double check whether your particular pump will be compatible with the vat of your choice.
For the most straightforward kind of hydro - one in which containers with your cannabis plants sit in a reservoir directly - a precise fit is required. Sine in this technique plants are kept constantly in bubbling water, extra care is needed to avoid any light reaching the solution - it will lead to algae growth, which in turn might severly affect both your plans and hardware. The same is true for any reservoir holding hydroponics or automatic irrigation nutrient solution - keep it in the dark!