stop pump from running if voltage drops below certain amount

sunstarter

Hey all. I've made a water fountain which only works properly if the full flow is being produced from the solar panel receiving good light. If the sun goes behind a cloud, the water becomes a trickle and the water feature doesnt work as it should. I'm just using one of those water feature solar pump kits in which there is a panel that connects directly to the pump. I'd like to put something on the line that will only switch the pump on if it is receiving enough voltage from the panel. I feel like that should be easy enough, but perhaps not? I have minimal electrical knowledge.