What is a Rectangular Fish Tank?
A rectangular fish tank is the classic box-shaped aquarium design with flat glass panels. Rectangular aquariums provide maximum swimming area, optimal gas exchange, and easy maintenance for aquatic hobbyists.
Learn more about aquarium size, horizontal tank design, and surface area in the PetMD freshwater aquarium guide.
Rectangular Aquarium Volume Formulas
Inches to US Gallons Formula:
Volume (US Gal) = (Length × Width × Height in inches) / 231
Centimeters to Litres Formula:
Volume (Litres) = (Length × Width × Height in cm) / 1,000
How to Measure Rectangular Aquariums
- Measure Inside Panel Length: Measure length from left glass inside edge to right glass edge.
- Measure Inside Panel Width: Measure front glass to back glass inside distance.
- Measure Water Level Height: Measure from glass bottom up to top water fill line.
- Divide by Conversion Factor: Divide cubic inches by 231 for US Gallons or cubic cm by 1,000 for Litres.
Rectangular Tank Numerical Walkthrough
For a rectangular fish tank measuring 36 inches long, 18 inches wide, and 12 inches high:
Cubic Inches = 36 × 18 × 12 = 7,776 cubic inchesVolume in US Gallons = 7,776 / 231 = 33.66 US GallonsVolume in Litres = 33.66 × 3.78541 = 127.42 Litres
Rectangular Aquarium Dimensions & Volume Chart
| Standard Tank Name | Dimensions (Inches: L × W × H) | US Gallons | Litres |
|---|---|---|---|
| 10 Gallon Standard | 20" × 10" × 12" | 10 gal | 38 L |
| 20 Gallon High | 24" × 12" × 16" | 20 gal | 75 L |
| 40 Gallon Breeder | 36" × 18" × 16" | 40 gal | 151 L |
| 75 Gallon Standard | 48" × 18" × 21" | 75 gal | 284 L |
| 90 Gallon High | 48" × 18" × 25" | 90 gal | 340 L |
Surface Area & Oxygen Exchange Benefits
Rectangular aquariums feature high surface-area-to-volume ratios, allowing optimal oxygenation across the water surface compared to narrow tall or spherical fish bowls.
Rectangular Aquarium Surface Area & Gas Exchange
Rectangular fish tanks offer a large surface area-to-volume ratio, facilitating oxygen exchange at the water surface. Sizing rectangular tanks accurately ensures sufficient swimming length and room for aquascaping decorations.