How to Drill a Hole in a Glass Aquarium the Easy Way

While most fish keepers start off with easy, off-the-shelf filters from the pet store, some hobbyists want to take their aquarium filtration to the next level. You can easily drain the aquarium water by drilling a hole at the top of your fish tank. The bulkhead, which is a waterproof plastic fitting that prevents it from leaking, allows you to pipe the water out and into an automatic water change system.

Each person has a different method of drilling glass tanks. We’ve tried all methods and have drilled hundreds more aquariums for our fish shop and personal fish rooms. This article explains the tried-and-true technique we eventually landed on. Drilling glass comes with its risks. We recommend that you wear safety equipment and that we are not held responsible for any injuries, loss, or damages that may occur during the DIY project. According to our experience, thicker glass is more likely to crack. Aquariums less than 40 gallons tend to have thinner glass, which can cause them to crack between 10 and 25% of the time.

Materials for drilling aquariums

– Glass aquarium that has not been tempered Bulkhead (slipx slip) – Diamond-tipped holesaw that matches the bulkhead’s size – Electric drill – Clamp – Pitcher or water bottle – Flat piece of wood about 1-inch thick. – Sharpie marker, pen – Painter’s tape ­ Pliers Safety glasses — Safety gloves

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While some aquariums have tempered glass on the bottom panel, they usually use non-tempered glass for the side walls. To test if the side walls are made of non-tempered glass, place a laptop or cell phone inside the tank so you can see its screen through the pane of glass that will be drilled. Make sure that the screen is white. Holding a pair of polarized glasses in your hands, look at the screen and rotate the sunglasses like you are turning a steering wheel. If the glass is not tempered, the screen will look like it is shifting from white to solid black as you rotate the sunglasses. If the glass has been tempered, the screen will show splotches and stripes when the sunglasses rotate. You can view video examples online that illustrate this effect.

Instructions for drilling Aquariums

1. Place the aquarium sideways so that the tank wall is facing upwards. The piece of wood should be aligned against the tank’s rim and side edges. Position the hole saw where you want the bulkhead to be and draw a dot in the center of the hole. The hole should be low enough so that (a) the overflow or drain is at the surface of the water and (b) the locking nut of the bulkhead won’t hit the rim while tightening it. You can also mark the wood so that you know which side touches the rim.

1. Take the wood off the tank and drill a hole in the wood where you marked the dot. (Ideally, you should use another hole saw that is meant for wood. You can use the diamond-tipped saw to do the job, but the wood might smoke. The guide is now used to make sure the hole saw doesn’t move when drilling. 2. Once the guide has been created, align the piece of wood against both the tank’s rim and the side edge. Then clamp it down. Tape the inside of the aquarium where you see the hole so that when the glass hole is drilled, it will not fall out and crack your tank. The tape helps to reduce chipping and makes the hole look clean.

1. You can fill the hole with water. Some of the water will leak out so you will need to keep refilling it to keep the glass sufficiently wet. Water helps to wash away the dust and keep the hole saw from overheating.

1. Press the trigger of the electric drill until it spins slowly. Then, gradually increase the speed to moderate. You should apply a light pressure on the holesaw, allowing the drill to move downwards. The hole saw should be kept level. Do not tilt the drill to make the hole uneven. The goal is to slowly file your way through the glass, so the drilling step may take up to 5-20 minutes, depending on the thickness of your tank.

1. Pour more water into the guide and onto the hole saw if the glass is making a loud squealing noise. Then continue drilling. 2. If the frequency of the grinding sound changes, it is likely that the glass hole has already or is nearing breaking through. There may be some slightly jagged edges on the hole, but the bulkhead’s gasket will cover them so no need to deburr the hole. Do not touch the glass hole’s interior.

Diagram for bulkhead fitting

1. The bulkhead is quite fragile so make sure to place the aquarium in its final position before you attach the bulkhead. The bulkhead should be inserted through the hole, so that the gasket and flanged head are on the tank’s inside and the locking nuts on its outside. Tighten the locking nut with your fingers and then finish cinching it down with pliers.

Congratulations on drilling the first aquarium! Last note: Make sure you use high quality hole saws that are regularly replaced. Our hole saws can drill approximately 8-10 tanks before they start to wear out. Your aquarium is more likely to break if you keep it in use for too long. If you plan on drilling many tanks, get a pack of multiple hole saws and save yourself the headache. You can also stock up on bulkhead fittings that our family uses in our aquariums and fish shop.