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. Wearing safety gear is a good idea. We are not responsible for any damages, injuries, or losses that you might experience during this DIY project. We have found that the more thick the glass is, the less likely it will crack. Aquariums with a volume less than 40gallons are made of thinner glass. They tend to break between 10-25% of all cases.

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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Some aquariums have tempered glass in the bottom, but they use non-tempered for the side walls. You can check the side walls of your aquarium by placing a computer or mobile phone in the tank. The pane of glass will be drilled so that you can view the screen. Make sure that the screen 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. 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. Line up the piece of wood against the side edge and the rim of the tank. The hole saw should be placed where the bulkhead will be. The hole should be positioned low enough that the overflow, drain, and locking nut of bulkhead don’t touch the rim when tightening them. You can also mark the wood so that you know which side touches 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 aquarium inside where you see the hole. This will ensure that it doesn’t fall out and cause damage to your tank when drilling the glass hole. The tape also helps reduce chipping so that the hole is fairly 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 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. Use a gentle, even pressure to the hole saw and allow the drill’s weight to pull it down. The hole saw should be kept level. Do not tilt the drill to make the hole uneven. The goal is to gently file through the glass. This step can take anywhere from 5-20 minutes depending on how thick your tank is.

1. Pour more water into the guide and onto the hole saw if the glass is making a loud squealing noise. Continue drilling. 2. The frequency of the grinding sound changes indicates that the glass hole is close to or has already been broken 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 of bulkhead fitting

1. The bulkhead is quite fragile so make sure to place the aquarium in its final position before you attach 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. Tighten the locking nut with your fingers and then finish cinching it down with pliers.

Congratulations on drilling your first aquarium! A final tip: make sure to use high-quality hole saws, and that they are replaced regularly. Our hole saws can drill approximately 8-10 tanks before they start to wear out. The longer you use your hole saw, the more likely the aquarium will break while drilling. Save yourself the hassle of drilling multiple tanks with a set of multiple holesaws. Stock up on the bulkhead fittings we use in our home aquariums and fish store.