What is a 120 gallon tank good for?
The 120 gallon is four feet long and a full two feet wide and tall. Aquascapers and reef keepers love the depth. Check your floor before you buy: filled, it weighs well over half a ton.
How much water does it really hold?
The label says 120 gallons (454 liters). That is the tank filled to the very brim, measured from outside the glass. In real life the glass, the gap at the top, the gravel and the decor take up room. A set-up 120 gallon tank holds about 102 gallons (386 liters). Use that smaller number when you dose medicine or water conditioner. Work out your exact water volume
How much does a 120 gallon tank weigh?
An empty glass 120 gallon tank weighs about 160 lb (75 kg). Filled, with gravel and a few rocks, it weighs about 1,190 lb (540 kg). That is as much as a grand piano, so use a stand made for aquariums, not ordinary furniture. The load on the floor under the tank is about 149 lb per square foot (730 kg/m²). Add your own stand and rocks
What size heater does it need?
The colder your room, the bigger the heater. These sizes hold the water at 78 °F (25.5 °C), right for most tropical fish.
| Your room | Heater to buy |
|---|---|
| Warm room, 73 °F (23 °C) | 2 × 100 W |
| Normal room, 68 °F (20 °C) | 2 × 200 W |
| Cold room, 63 °F (17 °C) | 2 × 250 W |
Check your own room and target temperature
What size filter does it need?
For a community tank, look for a filter rated at 410–610 GPH (1,550–2,300 L/h). That moves all the water through the filter four to six times an hour. Goldfish and big cichlids need more. Size a filter for your kind of tank
How much gravel or sand?
| Depth | Gravel | Sand |
|---|---|---|
| 1 in (2.5 cm) | 62 lb28 kg | 66 lb30 kg |
| 2 in (5 cm) | 123 lb56 kg | 132 lb60 kg |
| 3 in (7.5 cm) | 185 lb84 kg | 197 lb90 kg |
Two inches suits most tanks. Rooted plants like three. Work it out in bags
How much water to change
A normal weekly water change is a quarter of the water: about 26 gallons (97 liters) for this tank. A big clean-up change is half: about 51 gallons (193 liters). Plan changes from your nitrate reading
How many fish can go in a 120 gallon tank?
It depends on which fish. The table shows how many of each the tank carries comfortably if that fish is the only kind in the tank. If you mix kinds, keep fewer of each.
| Fish | How many | Keep at least |
|---|---|---|
| Neon tetra | 60 or more | 6 |
| Guppy | up to 55 | 3 |
| Bronze corydoras | up to 42 | 6 |
| Molly | up to 20 | 3 |
| Tiger barb | up to 39 | 8 |
| Yellow lab | up to 20 | 4 |
| Angelfish | up to 4 | 1 |
| Boeseman's rainbowfish | up to 17 | 6 |
| Discus | up to 8 | 5 |
| Oscar | 1 | 1 |
Build your own fish list for this tank
Fish that need a bigger tank
These fish are often sold for tanks this size, but they outgrow it:
- Common pleco: grows to 16 in (40 cm) and needs at least 150 gallons (570 liters).
- Bala shark: grows to 14 in (35 cm) and needs at least 150 gallons (570 liters).
- Clown loach: grows to 12 in (30 cm) and needs at least 150 gallons (570 liters).
Questions and answers
What are the dimensions of a 120 gallon tank?
A standard 120 gallon glass tank is 48 × 24 × 24 inches (122 × 61 × 61 cm), measured on the outside as length × width × height. Brands differ by up to half an inch.
How much does a 120 gallon tank weigh?
Empty, about 160 lb (75 kg). Filled with water, gravel and rocks, about 1,190 lb (540 kg). Add the weight of the stand to find the load on your floor.
What size heater does a 120 gallon tank need?
In a normal room at 68 °F (20 °C), 2 × 200 W holds 78 °F (25.5 °C). In a cold room use 2 × 250 W; in a warm room 2 × 100 W is enough.
How many fish can I put in a 120 gallon tank?
It depends on the fish, not just the gallons. As the only kind in the tank, a 120 gallon tank carries about 60 or more neon tetras, or 55 guppies, or 42 bronze corydoras. Mixed tanks hold fewer of each.
How many liters is a 120 gallon tank?
120 US gallons is 454 liters. Once set up with gravel and decor, the tank holds about 386 liters (102 gallons) of water.
Other tank sizes
Dimensions are the common North American and European standard sizes; brands differ slightly. Weights assume standard glass of typical thickness, 4 cm of gravel and light rockwork. How we calculate