Drilled tanks and bulkheads question

[FishStarter89]

Can someone explain the purpose of drilling tanks for bulkheads? I know it has something to do with sumps but I'm having difficulty understanding the purpose of drilling to run output/input directly into the tank as opposed to running it over the back into the tank.

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[nelix10]

I think more about the drain! Over the glass requires sucktion to maintain flow!

 

[jeffaquarius]

Drilled tanks are safe from flooding your floor while hang on box overflow if not configured properly flooding will occur at your sump specially during power outages.

 

[mr_X]

One works by gravity- a constant. The other that goes over the top works by siphon. It's always better to drill for a drain. Returns can come over the top. the only reason I would drill for a return is if I was going to showcase the tank from the top. A rimless tank would be a good reason to drill a return hole.

 

[jeffaquarius]

When your siphon stops working in a non drilled tank you will have your return pump keeps pumping your sump water overflowing your display tank until sump runs dry and pump burns out.