Innovative Marine NUVO 20

Key stats

How many gallons is a 21 × 16 × 14 in tank?

A 21 × 16 × 14 in aquarium contains 20 US gallons by outside dimensions. The math:

21 × 16 × 14 = 4704 in³
4704 ÷ 231 in³/gal = 20.36 US gal
20.36 × 3.785 = 77.1 L

In practice, actual water capacity is 18 gallons after subtracting 0.375" of glass thickness on each side. Manufacturers typically market this as a 20-gallon tank for round-number simplicity.

For a different shape (cylinder, hex, bow-front) or to enter custom dimensions, use the full aquarium volume calculator.

How much does a filled 21 × 16 × 14 in tank weigh?

• Saltwater reef (with ~18 lb live rock + 1" sand bed): 239 lb (108 kg)
• Freshwater (with 20 lb gravel, no rock): 218 lb (99 kg)
• Empty glass only: approximately 46 lb
• Floor load: 102 lb/ft² (saltwater filled)

Floor-load warning: at 102 lb/ft², this tank exceeds the 40 lb/ft² typical residential live-load rating. Place over a load-bearing wall or get a structural assessment before installing upstairs.

Full breakdown including equipment, sump, and custom rock weight: aquarium weight calculator.

Glass thickness for a 21 × 16 × 14 in tank

Using the Wisner hobby formula with a 3.8 safety factor, this tank requires:

• Annealed (regular float) glass: 8 mm minimum (0.315")
• Tempered glass: 4 mm minimum (tempered is ~4× stronger than annealed)

Most commercial tanks at this size ship one thickness step up for additional safety. See the glass thickness calculator for the full formula and Starphire (low-iron) options.

Heater wattage for a 21 × 16 × 14 in tank

In a warm room (~70 °F ambient) targeting 78 °F, this size tank needs about 71 W of heating. The conservative reefkeeping practice is to run two heaters at 50 W each: if one fails stuck-on, the other isn't powerful enough to cook the tank alone; if one fails stuck-off, the remaining one slows the temperature drop while you replace it.

For cold-room or cool-basement adjustments: heater wattage calculator.

How much sand or gravel for a 21 × 16 × 14 in tank?

• 2" sand bed: ~33 lb of CaribSea Special Grade aragonite (2 × 20-lb bags)
• 4" deep sand bed (DSB): ~66 lb
• 1" shallow / aesthetic: ~17 lb

Other substrate brands (Nature's Ocean, Tahitian Moon, Eco-Complete): substrate calculator.

FAQ

How many gallons is a 21 × 16 × 14 in tank?

A 21 × 16 × 14 in aquarium holds approximately 20 US gallons by outside dimensions (77.1 L). After subtracting a standard 0.375" glass thickness on each interior wall, the actual water capacity is about 18 US gallons.

How much does a filled 21 × 16 × 14 in tank weigh?

A 21 × 16 × 14 in saltwater reef tank with ~18 lb of live rock and a 1" sand bed weighs about 239 lb (108 kg) filled. Freshwater with no rock comes in lighter, around 218 lb. Floor load is roughly 102 lb per square foot — most residential floors are rated for 40 lb/ft² live load, so confirm before placing upstairs.

What glass thickness do I need for a 21 × 16 × 14 in tank?

Using the Wisner hobby formula with a 3.8 safety factor, a 21 × 16 × 14 in tank needs at least 8 mm annealed (regular float) glass. Tempered glass can be 4 mm and still meet the same safety margin. This is the calculated minimum — most commercial tanks at this size ship with one step up for safety. See the glass thickness calculator for the full math.

What size heater for a 21 × 16 × 14 in tank?

For a tank in a warm room (~70 °F ambient), this size needs roughly 71 W of heating. For redundancy, run two heaters at 50 W each — heaters fail, and a single point of failure on tropical fish or coral is expensive.

How much sand or substrate for a 21 × 16 × 14 in tank?

A 2-inch sand bed in this footprint (21" × 16") needs approximately 33 lb of CaribSea Special Grade aragonite, or about 2 20-lb bags. For a deep sand bed at 4 inches, double that.

Is a 21 × 16 × 14 in tank good for a reef?

Yes — the 21 × 16 × 14 in footprint is well-suited to a reef tank. The narrow front-to-back depth limits aquascape complexity — possible for a reef, but expect to keep rock structures simple. Tank height is shallow — easy on lighting but limits vertical aquascape.

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