Fish by tank size

Choose your tank to see the fish that suit it, example stocking plans and what to avoid.

Bigger tanks are easier, not harder: more water dilutes waste and keeps temperature stable. For a first tank, 20 gallons or more gives you the most room for mistakes.

Tank	Typical size (in)	Litres	Water weight	Suitable species
3 gallon	12 × 8 × 10	11 L	25 lb	0
5 gallon	16 × 8 × 10	19 L	42 lb	7
10 gallon	20 × 10 × 12	38 L	83 lb	29
15 gallon	24 × 12 × 12	57 L	125 lb	45
20 gallon	24 × 12 × 16	76 L	167 lb	67
20 gallon long	30 × 12 × 12	76 L	167 lb	87
29 gallon	30 × 12 × 18	110 L	242 lb	95
40 gallon	36 × 18 × 16	151 L	334 lb	109
55 gallon	48 × 13 × 21	208 L	459 lb	128
75 gallon	48 × 18 × 21	284 L	626 lb	139
125 gallon	72 × 18 × 21	473 L	1043 lb	145

Have a different size? Enter it in the stocking calculator, or work out your volume with the aquarium calculators.