You don't need a drilled tank to have a sump. I'll explain the other methods but there's two things you should UNDER NO CIRCUMSTANCE....EVER....use to drain water to the sump
Do not use a siphon or use a pump to drain the water to the sump. You will NEVER be able to match the flow of that and your return pump perfectly. Without 24/7 supervision, you WILL flood your house. You may have already guessed that, but I have to make sure.
Now for solutions, you can buy a hang on overflow, or build one out of PVC. The pre-made one can be QUITE costly. A simple pvc one takes up less space, can work just as good if not better (if made properly) and can easily be painted to match your background so you can hardly tell its there (krylon fusion paint is supposed to safe for in tank use)
Just google or youtube DIY PVC overflow and you will figure it out
The point of an overflow is, they are designed so they can only drain as much water as what is being pumped into the tank....if your pump is putting in 400GPH, the drain will drain at 400GPH. Use at least 3/4" . I cannot tell you the drain rates of each diameter, however, I made the mistake of using 1/2" pvc and was getting 97GPH, which may be good enough for a 10 gallon tank =P. The larger the ID of the PVC has a somewhat exponential affect on the flow; 1" pvc isnt twice as much as 1/2", its about 6 times as much.
Unless you run an aqualifter pump, after time theres a chance your overflow devices can fail though, air bubbles may find its way inside your overflow and it will cease to drain water. When you find the PVC overflow guide, and I would actually check youtube, they have some good guides, you will see where they attach vinyl tubing to suck out air. And that's what the aqualifter pump attaches to.
All that aside, drilling a tank is supposed to be really easy, there are plently of good guides. All you need is a diamond tipped holesaw, some plumpers putty, and a bottle of water. I am actually planning on drilling my tank when my hole saw arrives. I bought it for 8 bucks on that big auction site. You may know this already, but you cannot drill tempered glass (maybe you can but I dont think you can do it with a simple hole saw)...just dont attempt it. Most glass tanks will only be tempered on the bottom, but to be sure you should contact the manufacturer of your tank.
Best of luck to you
