The Number I Look at Before Tank Volume
Aquarium glass gets thicker as water level rises because hydrostatic pressure increases directly with water depth, while the resulting bending stress and deflection of the glass panel increase much more aggressively than the pressure number alone suggests. At 50 cm water depth, bottom pressure is about 4.9 kPa ; at 80 cm it is about 7.8 kPa ; at 100 cm it reaches roughly 9.8 kPa .
That pressure is also permanent. Pilkington's technical guidance for aquaria notes that water applies a constant but non-uniform load to glass—the deeper the water relative to the panel, the greater the pressure—and that glass design must account for the long-duration nature of this loading. ASTM E3401 likewise treats hydrostatic loading and the time-dependent behavior of glass as specific design considerations for laminated glass used in pools and aquariums.
So when a buyer sends Ruibit a custom aquarium inquiry, “500 gallons” is not the first structural number I want.
Give me the water height.
Then the unsupported panel length.
Then tell me whether the tank is rimless, braced, framed or laminated.
Now we can talk about glass.
50 cm and 100 cm Do Not Mean “Twice the Same Tank”
Hydrostatic pressure follows a simple relationship:
P = ρgh
where:
ρ
= water density
g
= gravitational acceleration, approximately 9.81 m/s²
h
= water depth
For freshwater, using roughly 1,000 kg/m³:
| Water Depth | Approx. Pressure at Bottom |
|---|---|
| 30 cm | 2.94 kPa |
| 50 cm | 4.91 kPa |
| 70 cm | 6.87 kPa |
| 80 cm | 7.85 kPa |
| 100 cm | 9.81 kPa |
| 120 cm | 11.77 kPa |
The top edge of the side panel sees almost no hydrostatic pressure.
The bottom sees the maximum.
So the load distribution looks roughly triangular.
This is the first thing that matters: doubling water depth doubles maximum hydrostatic pressure.
But this is where buyers sometimes make the wrong leap:
“If pressure doubles, shouldn't the glass only need to be a little thicker?”
No.
The glass panel also has to resist bending .
That changes the calculation substantially.
I Care About Bowing Before I Care About Breaking
Glass does not have to crack before I dislike a design.
Take a long front panel and fill the tank.
The center of that panel moves outward slightly.
That is deflection.
A properly engineered amount can be acceptable. Excessive deflection is not something I want to discover after the aquarium reaches the customer's living room.
The established aquarium plate-calculation method published by Aquarium World uses water height cubed in its side-panel thickness relationship:
t = √(β × H³ × 0.00001 / B)
where β reflects panel aspect ratio and B is allowable bending stress. The method uses 19.2 MPa as the tensile-strength value for ordinary annealed glass and, in its worked approach, a safety factor of 3.8 .
Don't use that equation as a DIY permission slip.
The useful purchasing lesson is what sits inside it:
water height has an outsized effect on required glass thickness.
That is why adding another 20 cm of height to a large aquarium can change the structural specification much more than the buyer expects.
Same Liters. Different Glass Problem.
Imagine two custom aquariums.
Tank A: long and relatively shallow.
Tank B: shorter but considerably taller.
We can manipulate length and width so they hold similar water volumes.
The glass does not care that the invoice calls both of them “1,000 L aquariums.”
Tank B has a taller water column.
Therefore its lower front and side panels see greater pressure.
This is why aquarium glass thickness should not be selected from gallons or liters alone . Pilkington's aquarium guidance specifically bases glass selection on liquid loading and water height, while noting that liquid density and additional dynamic loads may also need consideration.
For a B2B buyer, this is one of the easiest ways to interrogate a suspicious quotation.
Ask:
“What water height did you use for the glass calculation?”
If the answer is:
“It's a 300-gallon tank, so we always use 15 mm,”
I would keep asking questions.
Panel Length Still Matters
Height is not the only number.
A 60 cm-high front panel that is 80 cm long does not behave exactly like one that is 250 cm long.
Long unsupported panels can flex more.
This is where aspect ratio, edge support and bracing enter the calculation. The Aquarium World method uses different coefficients according to the ratio between panel length and height.
So the structural conversation is really:
water height + unsupported span + glass type + support condition + bracing + safety factor
not:
liters = glass thickness
This is also why a center brace can matter so much. It changes how the long front and rear panels are supported and reduces the effective unsupported span.
Rimless Is Not Just a Style Choice
Now remove the top brace.
The aquarium looks cleaner.
Architecturally, I understand the appeal.
Structurally, however, we have changed the boundary conditions of the glass panel.
A rimless front panel has less restraint at its upper edge than a properly engineered braced system. That can increase deflection and influence the thickness required to achieve the desired structural margin.
So when Ruibit receives an RFQ saying:
2000 × 700 × 700 mm, low-iron glass
I still don't have enough information.
Is it rimless?
Euro-braced?
Cross-braced?
Framed?
What is the actual operating water height—700 mm, or perhaps 650 mm after freeboard?
Where are the overflow openings?
How is the bottom supported?
Those details can turn two aquariums with identical external dimensions into different structures.
Low-Iron Glass Does Not Cancel the Structural Calculation
This deserves repeating because “ultra-clear” gets treated as though it were a strength grade.
It isn't.
Low-iron glass is primarily an optical specification . It reduces the green coloration associated with conventional float glass and improves color neutrality.
Glass thickness remains a structural decision.
Likewise, a beautifully polished edge does not compensate for an under-designed panel.
For large aquariums, the specification needs to keep separate questions separate:
Optics: low-iron or standard clear?
Structure: thickness, lamination, bracing and support?
Bonding: joint geometry and structural silicone?
Manufacturing: edge quality, dimensional tolerances and assembly?
That separation makes quotations much easier to compare.
What I Would Ask the Manufacturer to Put on the Drawing
If I were buying custom large aquariums from Ruibit—or auditing any aquarium factory—I would want the approved technical drawing to state:
Actual operating water height:
___ mm
Front panel dimensions:
___ × ___ mm
Glass thickness:
___ mm
Glass type:
annealed / heat-treated / laminated as designed
Low-iron viewing panels:
identified individually
Bracing system:
rimless / Euro-brace / cross-brace / frame
Bottom support condition:
specified
Silicone joint geometry:
defined
Design/safety basis:
declared by manufacturer
Overflow penetrations:
shown on drawing
Production water test:
required before shipment
I would also ask whether the manufacturer changed glass thickness after the customer increased the tank height during design revisions.
That catches more than you might think.
A customer starts with 600 mm.
The architect changes it to 750 mm because the taller tank looks better in the rendering.
Somebody updates the CAD dimensions.
Nobody revisits the glass.
That is exactly the kind of “small design change” that is not small.
I also checked the Ruibit Alibaba storefront supplied for this article. The publicly retrievable store information was not detailed enough for me to verify current model-specific structural glass schedules, so I would not invent a Ruibit thickness chart here. For an actual order, the thickness should be confirmed from the approved project design.
The Cheapest Extra 20 cm Is on the Rendering
This is something I would tell an architect before the glass order is released.
Making an aquarium taller looks almost free in CAD.
Drag the top line upward.
Done.
At the factory, that extra height can mean thicker glass, more glass weight, heavier handling, different bracing, greater silicone-joint loads, a stronger cabinet and more difficult maintenance.
Pilkington's guidance captures the physics neatly: the greater the water height, the greater the pressure applied to the glass.
The rest of the aquarium has to live with that decision for years.
So when comparing two custom aquarium quotations, don't ask only:
“How many millimeters of glass are you using?”
Ask the better question:
“Why is that thickness appropriate for this water height, this unsupported span and this bracing design?”
A trustworthy manufacturer should be able to explain the answer.
Thick glass is not the engineering. The engineering is knowing why it needs to be that thick.
