u can use a sump like warorks15 said all u need to do is have a hole in your return line to prevent a backwards siphon. the hole creates a break in the siphon so it will only drain until the break point. another good way is to have your return hose connected to a u tube of some sort. u can make this out of
pvc quite easily, and can make it to any size/length you want. have it end near the top of the tank or whatever level you want the siphon to break. if you were ever to get a backwards siphon it will siphon to the water level and the tube and stop. just make sure your sump can handle the extra water that would siphon out of the main tank. plumbed and set up properly it will never overflow. just be sure u dont have any leaks...
hth