Abstract: Coral reef display tanks and restaurant Seafood Display Tanks look similar. They're both glass boxes with water. But structurally, they're completely different. A reef tank has 1-2 feet of water depth. A seafood display tank has 3-5 feet. That extra depth changes everything: glass thickness, bracing requirements, bottom support, and load distribution. After designing structural systems for 40+ custom tanks, I can tell you: a reef tank design will leak in a seafood display, and vice versa. The water pressure doesn't care what you're keeping in the tank.
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Two tanks. Same length (2 meters). Same width (1 meter).
One is a reef display. One is a seafood display.
They look the same. Glass walls. Clear water. Beautiful fish.
But if you put a reef tank design in a restaurant? It will crack.
If you put a seafood display in a reef tank? The fish will hit the glass.
Why? Because they're structurally different. Let me show you.
The Depth Problem
Here's the key difference: water depth.
Reef display tank: 60cm water depth.
- Water pressure at the bottom: ~6 kPa
- Glass thickness: 12mm on viewing panels
Seafood display tank: 120cm water depth.
- Water pressure at the bottom: ~12 kPa
- Glass thickness: 19mm on viewing panels
That's double the depth. Double the pressure. Double the glass thickness.
That's the difference between a reef tank and a seafood display.
The Glass Thickness Calculation
Here's how I calculate glass thickness.
For a vertical glass panel under hydrostatic pressure:
Required thickness = sqrt((Pressure × Span²) / (Allowable stress))
Let me show you the numbers.
Reef tank (60cm depth):
- Pressure at bottom: 6 kPa
- Panel span: 1 meter
- Required glass thickness: ~10mm
- We spec: 12mm (with safety factor)
Seafood display (120cm depth):
- Pressure at bottom: 12 kPa
- Panel span: 1 meter
- Required glass thickness: ~14mm
- We spec: 19mm (with safety factor)
That's why seafood displays need thicker glass. The water pressure doubles. The required thickness goes up by 40%.
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The Bracing Requirement
This is where most people go wrong.
A reef tank (60cm deep) can use a simple top brace. The pressure is low enough that a single brace across the top works.
A seafood display (120cm deep) needs more. It needs:
- Top bracing across the entire width
- Middle bracing at 60cm height
- Bottom support across the entire footprint
Without middle bracing? The glass bows. It cracks. It leaks.
I've seen restaurant seafood displays installed without middle bracing. They look fine on day 1. They start bowing on day 30. They crack on day 90.
The Bottom Load
This is the other one people forget.
A reef tank (60cm deep) weighs about 1,200 kg for a 2m × 1m tank.
A seafood display (120cm deep) weighs about 2,400 kg for the same footprint.
That's double the weight. The floor needs to support it.
Most residential floors are rated for 300-500 kg/m². That's enough for a reef tank.
It's not enough for a seafood display. You need structural support. Steel beams. Reinforced concrete.
I've seen seafood displays installed on residential floors. The floor sagged. The tank cracked.
The Silicone Joint Width
This is the subtle one.
For a reef tank (60cm deep):
- Silicone joint width: 5-6mm
- Joint depth: 12mm (full glass thickness)
For a seafood display (120cm deep):
- Silicone joint width: 8-10mm
- Joint depth: 19mm (full glass thickness)
The silicone joint needs to be wider for deeper tanks. Why? Because the glass flexes more. A wider joint absorbs the movement.
A narrow joint on a deep tank? It cracks. It leaks.
What I'm Not Going to Tell You
I can tell you how thick the glass needs to be. I can tell you how much bracing is required. I can tell you how much the tank weighs.
But I'm not going to tell you which coral to keep. I'm not going to tell you how to set up the filtration. I'm not going to tell you how to maintain the seafood system.
That's not my department. I design the structure. You fill it with water and fish.
The 40-Tank Lesson
I've designed structural systems for 40+ custom tanks.
The customers who ask "how thick should the glass be?" They get a tank that lasts.
The customers who say "it looks fine" They get a tank that leaks.
The water pressure doesn't care what you're keeping in the tank. It just pushes. If the glass can't handle it? It breaks.
What We Spec at Ruibit
When we design a custom display tank at Ruibit, we don't use one-size-fits-all.
We ask: "What's the water depth? What's the panel span? What's the floor load rating?"
Then we calculate the glass thickness. The bracing. The bottom support.
For a reef display? 12mm glass. Simple bracing. For a seafood display? 19mm glass. Full bracing.
That's what we've learned from 40+ tank designs. The customers who do the structural calculations first? They get a tank that lasts. The customers who just pick a size? They come back 6 months later with a cracked tank.
The Two Tanks
The two tanks are on my drawing board.
Same length. Same width.
But different depths. Different glass. Different bracing.
They look the same. They're structurally completely different.
The water pressure doesn't care what you're keeping in the tank. It just pushes.
