A hydroponic robot is less about moving parts and more about repeatable plant care. The core loop is sensing pH, nutrient strength, water temperature and reservoir level, then dosing small corrections with peristaltic pumps. The robot is the grow assistant, not a humanoid gardener.
The biggest practical issue is sensor drift. Cheap pH probes need calibration and storage solution; EC probes need temperature compensation. Do not let firmware blindly dose forever based on one bad reading. Use limits, delays and alerts before adding chemicals.
Start with monitoring and LED scheduling before closed-loop dosing. Once readings are stable for a week, add small peristaltic pumps for pH up/down and nutrients. A camera timelapse is optional, but it makes failures obvious: drooping plants tell you more than a dashboard sometimes.