I dabbled in hydroponics for some years. Due to my inability to get my Rasberry Pi and Arduino working I ended up using a 12V pump and one of those cheap $10 electric timers on Aliexpress. I estimated how much time it took for my hydroponics system to drain and that's what I set on the timer. Other people I followed had all sorts of sensors rigged up, which I would have done if I had the time and skill but I failed, so in the end it was just the timer. I too had single solar panel and battery and the system worked for over 7 years with no issues. I just replaced the pump once or twice.