Putting a drill against a glass aquarium can feel intimidating, but trust us, it's easier than you think. With the right diamond hole saw, careful preparation, and a little patience, you can cut a clean hole for an overflow, return line, or bulkhead in no time.
Why Drill Your Own Aquarium?
A predrilled aquarium is convenient, but the location of the overflow and return lines has already been decided for you. Drilling the aquarium yourself gives you more freedom to customize the system.
You can position an external overflow where it makes the most sense, add return lines in your preferred locations, and select plumbing components that match your specific filtration setup.
Starting with a standard glass tank and drilling it yourself can also save you some money, which is another way of increasing your coral budget later!
Tools and Supplies You’ll Need
Gather everything before you begin. Having to stop halfway through the process to go on a hardware store run is the worst.
Drilling Equipment
- Variable-Speed Drill
- Correctly Sized Diamond Coated Hole Saw
- Drilling Guide (if available)
- Tape Measure
- Marker
- Eye Protection
Setup and Cleanup Supplies
- Plumber’s Putty
- Masking Tape (optional, but helpful)
- Clean Water
- Towels
- Flat, Padded Work Surface
- Equipment Being Installed (i.e. overflow box, bulkhead, return nozzle, etc.)
Choose the Hole Saw Based on the Bulkhead
Bulkheads are commonly labeled according to the pipe size they accept, not the diameter of the hole required in the glass. Always check the bulkhead manufacturer’s recommended hole size before selecting a diamond hole saw.
Learn More: How to Size Bulkhead Fittings
Step 1: Confirm the Glass Is Safe to Drill
Never Attempt to Drill Tempered Glass
Tempered glass cannot be drilled. Attempting to drill it will cause the entire panel to shatter.
Contact the aquarium manufacturer whenever possible and confirm whether the specific panel you plan to drill is tempered. Do not assume every panel on the aquarium uses the same type of glass. Some aquariums may have a tempered bottom panel with drillable side panels, while others may use tempered glass throughout.
The aquarium should be empty, clean, and dry before drilling. Inspect the area closely for cracks, deep scratches, large chips, or other damage. Drilling near existing damage can increase the risk of the crack spreading across the panel.
Step 2: Plan and Mark the Hole Location
Determine exactly where the hole needs to go before making any permanent marks. Account for the aquarium trim, nearby holes, overflow box dimensions, and the complete size of the bulkhead.
Remember that the pipe diameter is only part of the installation. You also need enough room for the bulkhead flange, gasket, retaining nut, elbows, fittings, and any plumbing that will be attached afterward.
Use the actual overflow, bulkhead, or return fitting to verify the layout. Check that the equipment is level, confirm that the plumbing will clear the aquarium stand, and make sure you can reach the bulkhead nut after the aquarium is installed.
Step 3: Support the Aquarium
Place the aquarium on a flat, level, and stable work surface. Whenever possible, position the tank so the panel being drilled is facing upward. This gives you better control over the drill and makes it easier to keep water around the cutting area.
The aquarium must be evenly supported. Make sure there are no uneven surfaces creating pressure points beneath the glass.
Place a folded towel beneath the drilling location. The towel helps catch the circular glass disc when the cut is complete and reduces the chance of it cracking the glass below.
Step 4: Prepare the Drilling Area
If you have a drilling guide, position it over the marked hole and gently clamp it in place. The clamps only need to keep the guide from sliding. Don't overtighten.
Create a small circular dam around the drilling area using plumber’s putty. Fill the dam with clean water before starting the drill. The water helps keep the glass and hole saw cool. A diamond hole saw should never be allowed to run dry while cutting aquarium glass.
Put on your eye protection, confirm that the drill’s hammer setting is turned off, and set the drill to a low speed.
Step 5: Drill the Glass
Final Aquarium Drilling Checklist
Before starting the drill, run through this checklist one final time:
- The specific glass panel is not tempered
- The aquarium is empty, clean, and dry
- The glass is free from cracks and major damage
- The diamond hole saw matches the bulkhead requirements
- The full bulkhead and plumbing layout has been checked
- The hole is clear of the aquarium trim
- The aquarium is evenly supported
- A towel is positioned to catch the glass disc
- The drill’s hammer mode is turned off
- The drilling area is filled with clean water
- Eye protection is being worn
- The drill is set to a low speed
1Position the Hole Saw
Place the diamond hole saw inside the drilling guide and hold the drill as straight as possible. Make sure the saw is centered over the marked location.
2Start at Low Speed
Begin drilling slowly and apply very light pressure. The goal is not to push the saw through the glass. The diamond coating gradually grinds away the material. It might feel like it's taking forever, but that's ok and normal. It should take several minutes to finish the hole.
Tip: If you don't have a drilling guide, hold the hole saw at a slight angle and allow one edge to create a shallow groove. Once the groove is established, slowly straighten the drill until the complete saw sits flat against the glass.
3Keep the Cutting Area Wet
Keep water around the hole saw during the entire cut. Occasionally lift the saw slightly while it is spinning slowly to allow fresh water underneath and clear away glass slurry.
4Avoid Sideways Pressure
Keep the drill steady and avoid rocking, twisting, or leaning the hole saw sideways. Uneven pressure can chip the opening or place additional stress on the panel.
5Ease Up Near the End
As the hole saw approaches the opposite side of the panel, reduce the pressure even further. Allow the last portion of glass to grind away gradually.
6Remove the Glass Disc
Once the cut is complete, stop the drill and carefully remove the circular glass disc. The disk will likely fall, which is why the towel placed below is so important.
Do Not Force the Final Breakthrough
Pushing the hole saw through at the end can cause the glass disc to break free suddenly and chip the back side of the opening. Slow down and use almost no downward pressure as the cut nears completion.
Also, don't stop and start the drill when you're close to breaking through. Keep the drill at a steady speed until your hole is complete or you'll risk the drill bit catching and damaging the glass.
Step 6: Inspect and Clean the Opening
Rinse away the glass slurry and inspect the opening from both sides of the aquarium panel. Look for cracks that extend away from the hole and inspect the area where the bulkhead gasket will sit.
A few small chips along the cut edge may occur, especially on the exit side. Minor chipping is pretty normal and shouldn't affect the seal of the gasket as long as the vast majority of the sealing surface is flat and undamaged.
The edges of the glass may be sharp, so try to avoid touching the edges of the new hole. Test-fit the bulkhead and confirm that it passes through the opening without being forced.
Thoroughly rinse the aquarium to remove all glass slurry and debris before installing any equipment. Repeat the same process for each additional opening.
Common Aquarium Drilling Mistakes to Avoid
- Attempting to drill tempered glass: Tempered glass will shatter when drilled.
- Choosing the hole saw based only on pipe size: The bulkhead opening is usually larger than the pipe it accepts.
- Forgetting about the aquarium trim: The bulkhead flange or nut may interfere with the frame.
- Placing holes too close together: Leave enough glass between openings and enough room for the fittings.
- Running the drill too fast: High speed creates additional heat and makes the drill harder to control.
- Allowing the saw to run dry: Water is needed to cool the diamond coating and remove slurry.
- Applying too much pressure: Let the diamond coating grind through the glass gradually.
- Rocking or twisting the drill: Sideways pressure can chip the glass or create an uneven opening.
- Forcing the final breakthrough: Reduce pressure as the saw reaches the opposite side.
- Overtightening the drilling guide: Clamps should only prevent movement.
Explore Aquarium Plumbing Supplies
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