Alright, so Ziggy commented on the skimmer thing - basically what's removed by the skimmer is so minimal it's not an issue.
Why 2 switches. Well, like Ziggy said it's a fail safe. The lower switch is set at my desired water level. The upper switch is just some arbitrary distance above. I set my upper one just to make sure the wiring from the lower didn't interfere with it.
Picture this. A snail gets into your sump. He decides to go checkout your switches, and gets himself lodged in the switch so that it can not float. The switch gets stuck in the lower position, telling your controller that you need water. The controller, eager to do his job, closes the relay supplying power to the pump. The pump springs into action, providing refreshing, clean RO
water into your sump. Yet, that pesky snail is still there, as the water level continues to rise, and rise, and rise.
So, the second switch is the fail safe. First switch gets stuck, second switch has it's back. Both switches must be down for the circuit to close and send electricity to the pump. If either switch is in the up position, power cannot be applied.
I know, lots of words for a simple explanation, but I don't want you to get bored around here.