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29 Gallon Tank Dimensions
A standard 29 gallon aquarium measures about 30 × 12 × 18 in (76 × 30 × 46 cm) on the outside. Exact sizes vary by brand: Aqueon lists 30¼ × 12½ × 18¾ in and Marineland 309⁄32 × 129⁄16 × 18¾ in. Once it's set up with 2 inches of sand, it holds roughly 24 gallons of water and weighs about 280 lb in total.
29 gallon tank calculator
Drawn to scale from your numbers: sand at the bottom, water up to your fill line.
Setting up a 29?
- Plan your fish: the stocking calculator checks numbers and tank mates
- Size your heater for your room temperature
- Check another tank's volume, any shape
Not every 29 gallon is the same size
The “29 gallon” label is a class of tank, not an exact measurement. Here is what each source actually lists:
| Source | L × W × H (in) | Empty | Full |
|---|---|---|---|
| Aqueon size chart | 30¼ × 12½ × 18¾ | 40 lb | 330 lb |
| Marineland ML10290 (dealer listing) | 309⁄32 × 129⁄16 × 18¾ | 38 lb | 280 lb |
| Tetra 29 gallon (Amazon listing) | 304⁄21 × 12½ × 18½ | 43 lb | – |
| Imagitarium open-glass 29 (Petco) | 304⁄21 × 122⁄5 × 2025⁄29 | – | – |
Checked 24 Sep 2026. Marineland's full weight is simply the label gallons × 8.34 lb plus the empty tank; Aqueon's is closer to the full outside volume filled with water. Neither includes sand, rock or the stand. That's why the two brands disagree.
Same stand, two tanks
The 29 and the 20 long share one 30¼ × 12½ footprint. The 29 is simply 6 in taller, so the same stand, lid and 30 in light fit both.
| Tank | L × W × H (in) | Outside volume |
|---|---|---|
| 20 gallon long | 30¼ × 12½ × 12¾ | 20.9 gal |
| 29 gallon | 30¼ × 12½ × 18¾ | 30.7 gal |
| 30 gallon (different stand) | 36¼ × 12⅝ × 16¾ | 33.2 gal |
Aqueon size chart.
The 30 gallon is 6 in longer than the 29, so despite the similar name it needs a 36 in stand, lid and light.
Why 29 gallons, not 30?
The 29 is the tall version of the 30 × 12 footprint that the 20 long made popular, which is why stands and lids for it are easy to find. The 30 gallon is a different, longer tank (36¼ in).
The extra height buys volume without floor space: a 29 needs the same 2.6 sq ft as a 20 long but holds about 27.0 gallons of water against the 20 long's 18.1 (bare bottom, our estimate). The trade-off is reach: at 18¾ in tall, planting and cleaning the bottom takes a longer arm or tools.
How much water a 29 gallon really holds
Multiply the outside dimensions of an Aqueon 29 and you get 30.7 gallons. You never get that much water, because of three things:
- Glass. With about 1/4 in glass (an estimate; check your tank), the inside is roughly 29¾ × 12 in.
- The gap at the top. Most people keep the water about an inch below the rim.
- Substrate. Two inches of sand takes up about 12 litres of space.
That leaves about 27.0 gallons with a bare bottom and 24.0 gallons with 2 in of sand. Use the real figure, not the label, when you dose medication or water conditioner.
Weight and stand
A set-up Aqueon 29 comes to about 281 lb: 40 lb of glass, about 200 lb of water and about 41 lb of sand, before rock and the stand itself. That sits on 2.6 square feet.
- A set-up 29 weighs about 281 lb. That's too much for most dressers and desks, so use a stand made for 30 × 12 tanks.
- Aqueon lists 330 lb full; add rock and decor on top of that when choosing a stand.
General guidance, not structural advice.
Equipment for a 29 gallon
| Item | Starting point | How we got it |
|---|---|---|
| Heater | 72–120 W | 3–5 W per gallon of real water; use the higher end in a cold room. |
| Filter | 96–144 gph | Turning over the water 4–6 times an hour |
| Sand, 2 in deep | ≈ 41 lb | Inside floor area × depth at about 1.6 kg per litre (estimate) |
| Light | 30 in | Match the tank length |
| Lid | 30 × 12 in | Check the maker's fit list |
Rules of thumb, not guarantees. Fish choice, room temperature and filter type all change the right answer.
What a 29 gallon is good for
The height suits a planted community tank and mid-sized schooling fish. Check any mix in the stocking calculator.
How the numbers are worked out
Worked examples
Aqueon 29, 1/4 in glass, 1 in gap, 2 in sand: inside 29.75 × 12 in, water height 18.75 − 0.25 − 1 − 2 = 15.5 in. 29.75 × 12 × 15.5 = 5,534 in³ ÷ 231 = 24.0 gal (90.7 L).
Marineland 29, 1/4 in glass, 1 in gap, 2 in sand: inside 29.78 × 12.06 in, water height 18.75 − 0.25 − 1 − 2 = 15.5 in. 29.78 × 12.06 × 15.5 = 5,568 in³ ÷ 231 = 24.1 gal (91.2 L).
Bare-bottom Aqueon 29, 1/4 in glass, 1 in gap, 0 in sand: inside 29.75 × 12 in, water height 18.75 − 0.25 − 1 − 0 = 17.5 in. 29.75 × 12 × 17.5 = 6,248 in³ ÷ 231 = 27.0 gal (102.4 L).
FAQ
How many gallons is 30 × 12 × 18?
30 × 12 × 18 in is 6,480 cubic inches, which is 28.1 US gallons (106 litres) measured from the outside. That's why it's sold as a 29.
Will a 20 gallon long lid fit a 29 gallon tank?
Yes. Both share the same 30 × 12 in footprint, so lids, stands and 30 in lights fit either.
How much does a 29 gallon tank with water weigh?
Aqueon lists 330 lb and Marineland 280 lb. Our estimate with 2 in of sand is about 281 lb before rock.
What are the dimensions of an Aqueon 29 gallon tank?
Aqueon's size chart lists 30¼ × 12½ × 18¾ in, including the trim.
How many litres is a 29 gallon tank?
29 US gallons is 110 litres. Set up, expect about 91–103 litres of actual water.
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Sources
- Aqueon aquarium size and weight chart, aqueon.com (PDF): www.aqueon.com
- Marineland standard aquariums, Bluefish Aquarium (dealer): bluefishaquarium.com
- Marineland 29 Gallon ML10290, Bluefish Aquarium: bluefishaquarium.com
- Tetra 29 Gallon Glass Aquarium, Amazon: www.amazon.com
- Imagitarium 29 Gallon Open-Glass Aquarium, Petco: www.petco.com
- Aquarium Weights & Sizes, SaltwaterAquarium.com: www.saltwateraquarium.com
- All accessed 24 Sep 2026. Calculations by TankRatio; “estimate” and “rule of thumb” figures are ours.