An acrylic aquarium tunnel is a pressure vessel that people walk through, and the design conversation starts with a single question: what is the water depth above the crown of the tube.
A public aquarium in Busan specified a 2200 mm tunnel through a 4.2 m deep tank. The first cost estimate assumed 80 mm walls; the hydrostatic calculation for that depth and diameter came out at 110 mm, and the difference was the entire project budget discussion.
Acrylic aquarium tunnel wall and depth
- Depth to 3 m, 2 m diameter: 60 to 80 mm
- Depth to 4.5 m: 90 to 110 mm
- Depth beyond 6 m: 130 to 150 mm
- Safety factor: 2.5 minimum on the calculated stress
Wall thickness is a depth calculation, and it must be calculated, not extrapolated from a smaller installation. The hoop stress in a tube grows with diameter and with depth, and a tunnel that is safe at 3 m is not the same as one at 5 m.
Joint sequence, saddles and flanges
Joints are made in the shop, one at a time, with full cure between operations. Each joint on a 110 mm wall takes days of controlled cure, which is why a tunnel is scheduled in sections and shipped as long as the road allows.
Saddle supports carry the tube weight without point loading the shell. A saddle every 2 m with a compliant pad distributes load; supports at 4 m spacing concentrate it at the contact line and the shell shows crazing there after a few years.
The flange to the concrete is where water finds a way. A flat face, an even gasket compression and a bolt pattern that keeps the load off the panel edge are the three things that decide whether a tunnel leaks in year one.
The panel casting and bonding side is covered in aquarium tank panels, and the sizing logic in what thickness for an aquarium.
Send your tunnel diameter, length and tank drawing to oversales@rpplexiglass.com for a cast panel and bonding quotation.
Frequently Asked Questions
What thickness acrylic aquarium tunnel walls?
60 mm for a 2 m diameter tunnel at 3 m depth, 100 to 150 mm for larger diameters or deeper installations. Depth and diameter together set the wall, never diameter alone.
How is a long tunnel joined?
Section by section in a controlled shop, each joint fully cured before the next. On-site bonding of 100 mm acrylic is unreliable because the joint cannot be annealed or inspected properly.
Why do tunnel flanges leak?
Mismatch between the tube and the concrete opening. A flange needs a flat face and a gasket compressed evenly; a 2 mm step in the concrete puts the load on one edge of the flange and the seal fails there.