Float Switch for Pump Shut Down

[Kaiser Tang]

I have recently installed an out door chiller. Basically it's a closed loop that goes outside and then back inside to my tank. Having that water going outside the tank worries me. Is there a float switch out there that will cut the power to a pump if the water falls below a certain level?

[Wrench]

http://www.automatedaquariums.com/js_599123.htm

[moumda]

Or this
http://www.aquahub.com/store/madisonms8000.html

[just dave]

Pump saver (http://www.championlighting.com/product.php?productid=17526&cat=0&page=6)