So you've realized how cool our overflow boxes are and want to drill your tank. Once you have your hole placement decided, you are ready to drill your glass (if you have a acrylic tank you can skip this section). You will want to lay the tank on its front to have the back lying horizontal. Be sure to protect the front of your tank from scratching. You will also want to be sure to put something like a piece of cardboard inside the tank under where you are drilling, the plug you drill out will likely fall through and could possibly crack the front. I want to note that we do not recommend drilling full tanks, although it has been done successfully. Your next step will be to make yourself a little reservoir around the holes using plumbers putty or Play Dough-type materials. Add some water and keep it there while drilling to keep the bit cool and lubricated. For your drill use of one with a clutch is best (a lot of cordless drills today have clutches, nobody ever uses the clutch). Set your clutch to its lowest setting, this will cause the bit to stop if it binds. A point must be made that drilling glass is actually grinding through glass, as such excessive pressure (more than a few pounds) should not be applied, let the bit do the work. Recommended speeds for drilling with the sizes we are dealing with here are 700-1000 rpm, just realize the faster you go the more your bit heats up and the fewer holes you will get out of it. Now you are ready to drill. Starting the hole is the hardest part and it is not difficult. Hold the drill and bit at a 45 degree angle on the edge of the hole you have marked, drilling with one hand and guiding with the other. Then you can start drilling. As you drill it will make a grinding noise, as you are literally grinding through it. As you start to get a groove forming on the edge start leveling your drill (perpendicular to the glass) out as you drill. Now your drill should be vertical and drilling the complete circumference of the hole. Keep your pressure light and water in the reservoir. You will get to a point of seeing water start to seep through, which means you are close. You will want to lighten up on any pressure here to minimize chip out on the other side. In all likelihood you will have some chip out, this is ok (even the manufactured tanks with drilled holes have chipout unless they finish the edge afterwards, which they very often don't). If you have another hole then repeat the whole process. Happy reefing, Mike Kirkman