Help with building sump please

[ccCapt]

I would play it safe and go with the 8" baffles. This way you are leaving yourself plenty of room for water to drain into the sump when the pump is shut down. You also won't have to worry about raising the skimmer and not having room to take off the cup. I have a 20g long sump for my 75 and when I shut my pump down I estimate about 8 gals drains into the sump. It's almost scarey....lol. When the pump is off my sump fills up to about 3" from the top.

 

[cmor1701d]

Many people drill small holes just below the water line. I found that just adjusting the outflow on the return I got the best results. The returns are under the water but high enough to ripple the surface, and the siphon breaks before the sump overflows (with about 2" to spare).

 

[fijiwigi]

Many people drill small holes just below the water line. I found that just adjusting the outflow on the return I got the best results. The returns are under the water but high enough to ripple the surface, and the siphon breaks before the sump overflows (with about 2" to spare).

So you don't drill the small hole? I still am trying to fully understand this. So if the return pump is pumping water into the tank what stops it from overflowing water into the main tank. I would think stopping the siphon on the overflow would cause the main display to overflow because it is no longer overflowing. If you have a pump feeding the water up the tubing to the main display siphon does not matter because the pump pushes the water. I want to control flow on the return as well did you put a ball-valve in the return line? I am still not to clear on the concept here. Can someone explain it to me like I am in kindergarden so I fully understand. How does stopping the siphon prevent overflow