Aquarium planning

Fish Tank Sizes & Dimensions Chart

Compare common aquarium footprints before choosing fish, equipment, and furniture. Dimensions vary by manufacturer; always measure the inside of your own tank before calculating volume or dosing water treatments.

Nominal size	Typical dimensions	Effective water	Approx. filled weight	Planning use
5 gallon	16 × 8 × 10 in	~4 gal effective	~60 lb filled	Small single-fish or invertebrate setups
10 gallon	20 × 10 × 12 in	~8.5 gal effective	~110 lb filled	A single betta or a carefully planned nano community
15 gallon	24 × 12 × 12 in	~13 gal effective	~160 lb filled	A small planted community with limited stocking
20 gallon long	30 × 12 × 12 in	~17 gal effective	~225 lb filled	Schooling fish and a balanced community layout
30 gallon	36 × 12 × 16 in	~26 gal effective	~330 lb filled	More room for groups and bottom dwellers
55 gallon	48 × 13 × 21 in	~47 gal effective	~625 lb filled	Larger communities; confirm floor and stand support

Effective water assumes roughly 85% of nominal capacity after substrate, hardscape, and an unfilled rim. Filled-weight estimates include water, glass, substrate, and basic equipment; use the linked calculators for your exact setup.

Choose footprint before volume

A long tank can be more useful than a tall tank for active schooling fish and for placing a heater, filter, and planting zones. Volume is only one part of stocking: adult size, social group size, activity level, filtration, and maintenance all matter.