90 gallon fish tank: dimensions, weight & setup
A standard 90 gallon tank measures 48 × 18 × 24 inches, holds about 79.8 gallons of real water and weighs roughly 870 lb once set up. It is a great size for tall planted displays, cichlid communities and reefs with more water on a 75’s footprint.
90 Gallon tank dimensions
| Inches | Centimeters | |
|---|---|---|
| Length | 48 in | 121.9 cm |
| Width (front to back) | 18 in | 45.7 cm |
| Height | 24 in | 61.0 cm |
| Footprint | 864 in² (6.0 ft²) | 5,574 cm² |
| Typical glass | 3/8 in | 10 mm |
These are typical outside dimensions for US glass tanks; brands vary slightly, so measure yours before buying a stand, lid or background.
How much water does it really hold?
| US gallons | Liters | |
|---|---|---|
| Outside dimensions | 89.8 | 339.8 |
| Filled 1 in below the rim | 79.8 | 302.2 |
| With 2 in of gravel | 72.8 | 275.5 |
Dose medication and fertilizer for the real water — about 73 gallons once the tank is aquascaped, not 90.
How much does a 90 gallon tank weigh?
| Empty (estimated, 3/8 in glass) | 150 lb | 68 kg |
|---|---|---|
| Filled with fresh water | 816 lb | 370 kg |
| Set up, fresh water + 2 in gravel | 872 lb | 396 kg |
| Set up as saltwater | 888 lb | 403 kg |
| Floor load under the stand | 145 lb/ft² | 7.0 kPa |
Add rock, decor and the stand (often 40–120 lb). A floor load of 145 lb/ft² is 3.6× the 40 lb/ft² a typical home floor is designed for when averaged over a room, so place the stand across the joists and near a load-bearing wall. Use the weight calculator to include your own rock and stand.
Heater size
| Room temperature (water at 78 °F) | Heater |
|---|---|
| 73 °F (5 °F lift) | 2 × 75 W |
| 68 °F (10 °F lift) | 2 × 150 W |
| 63 °F (15 °F lift) | 2 × 200 W |
See the heater size chart by tank or size your own in the heater calculator.
Plan maintenance with the water change schedule: a 30% change on this tank is about 21.8 gallons.
Filter flow
| Tank type | Real flow | Filter rating |
|---|---|---|
| Community tropical | 319–479 GPH | 456–684 GPH |
| Planted tank | 399–639 GPH | 570–912 GPH |
| Goldfish, cichlids or heavy feeders | 639–798 GPH | 912–1,140 GPH |
Substrate
| Depth | Gravel | Sand |
|---|---|---|
| 1 in (2.5 cm) | 47 lb | 46 lb |
| 2 in (5.1 cm) | 94 lb | 91 lb |
| 3 in (7.6 cm) | 141 lb | 137 lb |
Stocking ideas
- 1 oscar + 1 bristlenose pleco (species-focused)
- 6 angelfish + 10 corydoras + 2 pearl gouramis + 1 bristlenose pleco
- 12 yellow lab cichlids in a rocky layout
Check any combination — including temperature and group size — in the stocking calculator.
Setup tips
- Shares the 48 × 18 inch footprint of a 75, so stands and lids interchange — but it is 3 inches taller.
- At 24 inches deep, a gravel vacuum with a long hose and a stable step stool are essential.
- Expect about 870 lb set up; check the floor before choosing a second-floor room.
FAQ
What are the dimensions of a 90 gallon fish tank?
A standard 90 gallon glass tank measures 48 × 18 × 24 inches (121.9 × 45.7 × 61.0 cm) on the outside, a footprint of 6.0 square feet. Brands differ by up to about half an inch.
How much does a 90 gallon fish tank weigh?
About 150 lb empty, 815 lb filled with water and roughly 870 lb set up with 2 inches of gravel, before rock, decor and the stand.
How many gallons does a 90 gallon tank really hold?
89.8 gallons by its outside dimensions, about 79.8 gallons (302 liters) filled an inch below the rim, and about 72.8 gallons with 2 inches of gravel.
What size heater does a 90 gallon tank need?
2 × 150 W to hold 78 °F in a 68 °F room; 2 × 75 W in a 73 °F room and 2 × 200 W in a 63 °F room.
How much gravel or sand for a 90 gallon tank?
About 47 lb of gravel per inch of depth: 94 lb for a 2-inch bed, or 91 lb of sand.
What filter flow does a 90 gallon tank need?
319–479 GPH of real flow for a community tank (4–6× turnover), so choose a filter rated about 456–684 GPH.