!!WARNING YOU CAN CRACK OR DESTROY YOUR TANK BY ATTEMPTING TO DRILL IT!! I hold No liability if you screw your tank up
!!! YOU CAN NOT DRILL A TEMPERRED GLASS TANK!!(many 55 gal sides are tempered)
What you need:
Glass cutting drill bit
Bucket (2 if possible)
Garden hose with water supply
First off mark your holes. I have been told you must be at least the size of the hole away from the edge of the glass. Here we used a sharpie to mark my tank:
Put tape on the back side of the hole, this prevents the glass from falling into the tank possibly breaking the glass, however at the same time you have to be careful that the drill bit doesn't go through the tape:
The 75 gallon was big enough that we were able to put a 5 gal bucket under the hole, in case the tape fails or we drilled through it. If you can't get something like that to catch the drilled glass disk, you can alway but a folded towel directly under it to catch it.
Get your drill, drill bit, and water hose.
I put the chord and plug of the drill into a bucket to prevent the plug from getting wet and lowering my chances of electrocuting myself. As an added bonus, I made sure that the drill was plugged into a GFCI plug, **which is highly recommended**.
Throughout drilling make sure there is enough water to rinse off all the glass dust, this prevents the glass dust from entering your lungs and it keeps the diamond tipped drill bit cool and sharp, we regulated the water flow to about a half gallon a minute. Also do not apply too much pressure to the bit! Allow the drill bit to do its job. Pay particular attention when you get close to the end. The more you press down the higher the risk of chipping the inside glass or even worse breaking the glass.
Line up the mark with the edge of the bit and score the glass. VERY SLOW SPEEDS!
Hint, it will be easier to score on a portion of the bit surface (i.e. hold the drill at an angle so only part of the bit touches)
Square the bit and once you have a good groove you can speed it up a bit.
Click on the picture below to watch the video:
As mentioned, when you near the end of the hole make sure you are barely putting pressure on the bit. When it’s done it should look like this: