Dimensions of a 29 Gallon Aquarium | Exact Size & Weight

A standard 29-gallon aquarium measures about 30 inches long by 12 inches wide by 18 inches tall, though outer dimensions vary slightly by brand.

If you’re planning a stand, canopy, or location for a 29-gallon tank, the numbers matter more than the name. The nominal capacity — 29 gallons — tells you the volume class, not the physical footprint. Whether you’re measuring for a cabinet or checking floor support, these are the dimensions that count.

Standard 29-Gallon Dimensions by Brand

The most commonly cited dimensions for a 29-gallon aquarium are 30 in × 12 in × 18 in (length × width × height). In metric terms, that’s roughly 76.2 cm × 30.5 cm × 45.7 cm. But manufacturers don’t all list the same numbers, and the difference usually comes down to trim and frame.

Aqueon, one of the most common brands in US stores, lists its 29-gallon tank at 30.25 in × 12.5 in × 18.75 in — slightly larger on every side. One retailer listing for the Aqueon Long Tank Aquarium, Black, 29 Gallons shows 30.3 in × 12.5 in × 18.8 in. Those extra fractions of an inch come from the plastic trim and frame that wrap the glass.

That gap matters when you’re matching a hood or stand. A canopy built to sit flush on a 30-inch tank may not clear a 30.25-inch frame comfortably.

How Much Does a 29-Gallon Tank Weigh Full?

The weight climbs fast once you add water, substrate, and décor. Water itself weighs about 8.34 pounds per gallon, so 29 gallons of water alone comes to roughly 241 pounds — before the glass, gravel, or filter.

That ~330-pound estimate for a fully equipped tank with stand is worth writing down before you choose a location. A standard floor can handle it, but a flimsy TV stand or an unleveled surface cannot. If you’re shopping for support, our tested roundup of the best stands for a 29-gallon aquarium covers options rated for the full loaded weight.

What the “29 Gallon” Label Actually Tells You

Three different numbers get confused here, and the mistake costs people money. Nominal capacity is the 29-gallon rating — the manufacturer’s advertised volume class. Outer dimensions are the physical size including trim. Actual water volume is what’s left after substrate and décor displace space.

That last number is notably lower than 29. Once you add gravel, hardscape, and equipment, real water volume lands in the 24–26 gallon range. That matters for two reasons: medication dosing and heater sizing both run off actual water volume, not the tank’s name.

Stand and Lid Compatibility: The Oversize Trap

The 29-gallon shares a general footprint class with the 20-gallon long — both are roughly 30 inches across — but that doesn’t make their hardware interchangeable. Brand trim differences of half an inch or more mean a lid or stand made for one can sit crooked on another. Aqueon’s own 29-gallon tank comes in model-numbered variants like the AQ10029 and SKU 510029, both listed as 30x12x18, and even those can differ in listed outer dimensions depending on the retailer.

Before you buy a canopy, hood, or cabinet, verify the exact manufacturer dimensions for your specific model number. Don’t size hardware from the “29 gallon” label alone — the trim overhang is exactly where fit problems show up.

FAQs

Are all 29-gallon tanks the same size?

No. The standard footprint is 30 in × 12 in × 18 in, but brands like Aqueon list outer dimensions that run slightly larger due to plastic trim and frame. Always verify the exact model number’s listed dimensions before ordering a stand or lid.

How much floor space does a 29-gallon tank need?

The tank footprint itself is roughly 30 by 12 inches, but the stand or cabinet will extend beyond that. With trim and frame overhang, plan for a surface at least a couple inches wider and deeper than the tank’s listed outer dimensions.

Can a 29-gallon tank sit on a 20-gallon long stand?

Sometimes, but not safely by default. Both share a similar length class, but trim differences of half an inch or more between brands can leave the tank unbalanced. Match the stand to your tank’s exact outer dimensions, never to the gallon label alone.