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 have drilled hundreds of aquariums for our fish store and personal fish rooms, so we’ve experimented with all of these methods. This article will explain the tried-and true technique that we finally settled on. However, drilling glass can be dangerous. We recommend wearing proper safety equipment, and we are not liable for any injuries, losses, or damages you may experience while undergoing this DIY project. We have found that the more thick the glass is, the less likely it will 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 is not tempered Bulkhead (slip x slip) – Diamond-tipped hole saw that matches the size of the bulkhead – Electric drill – Clamp – Pitcher or bottle of water – Flat piece of wood that is about 1-inch thick – Sharpie marker or 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. You should ensure that the screen of your device is white. While holding a pair polarized sunglasses in each hand, you can look at the device’s screen. Next, rotate the sunglasses like a steering-wheel. The screen will appear as if it isn’t tempered. It will shift from white to black when you rotate the sunglasses. If the glass has been tempered, the screen will show splotches and stripes when the sunglasses rotate. Look online to see video examples that demonstrate this effect.

Instructions for Drilling Aquariums

1. Place the aquarium so that the tank wall will face upwards. Place the piece of wooden against the tank’s side edge. 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. Also, mark the wood so you know which side of the wood is touching the rim.

1. Drill a hole in the wood at the spot you have marked with a dot. You should prefer to use a hole saw designed for wood. If you decide to use the diamond-tipped hole saw, it will do the job but the wood may smoke a bit.) The wood now serves as a guide so that the hole saw will not move while drilling. 2. Once you have created the guide, place the wood piece against the tank’s side edge and rim again. 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. Water should be poured into the guide hole. You will have to refill the hole with water as some of the water may leak out. Water is used to remove dust from the hole saw and prevent it from heating up.

1. Press the trigger of the electric drill until it spins slowly. Then, gradually increase the speed to moderate. Apply a light, even pressure on the hole saw, and let the weight of the drill to carry it downward. Plus, try to keep the hole saw completely level and do not let the drill tilt or else the hole may get cut unevenly. 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. If the glass starts making a squealing sound, pour more water on the hole saw and into the hole in the guide. Then continue drilling. 2. The frequency of the grinding sound changes indicates that the glass hole is close to or has already been broken through. Although there may be some edges that are slightly jagged, the bulkhead’s gasket will completely cover them. Do not touch the glass hole’s interior.

Diagram of bulkhead fitting

1. The hole is somewhat fragile, so place the aquarium in its final location before installing the bulkhead. Insert the bulkhead through the hole so the flanged head and gasket are on the inside of the tank and the locking nut is on the outside. Use your fingers to tighten the locking nuts and then use pliers to finish cinching them down.

Congratulations on drilling the first aquarium! A final tip: make sure to use high-quality hole saws, and that they are replaced regularly. The hole saws that we purchased can drill 8-10 tanks before the blades wear down. The longer you use your hole saw, the more likely the aquarium will break while drilling. You can save time and headaches if you are drilling multiple tanks. You can also stock up on bulkhead fittings that our family uses in our aquariums and fish shop.