What is a 125 gallon tank good for?
The 125 gallon is six feet long. That length suits big, active fish: large rainbowfish, a group of silver dollars, or a Lake Malawi cichlid colony. It needs a strong stand that supports the whole base.
How much water does it really hold?
The label says 125 gallons (473 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 125 gallon tank holds about 106 gallons (402 liters). Use that smaller number when you dose medicine or water conditioner. Work out your exact water volume
How much does a 125 gallon tank weigh?
An empty glass 125 gallon tank weighs about 140 lb (65 kg). Filled, with gravel and a few rocks, it weighs about 1,220 lb (555 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 136 lb per square foot (660 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 430–640 GPH (1,600–2,400 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) | 70 lb32 kg | 74 lb34 kg |
| 2 in (5 cm) | 139 lb63 kg | 148 lb67 kg |
| 3 in (7.5 cm) | 208 lb95 kg | 222 lb101 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 27 gallons (101 liters) for this tank. A big clean-up change is half: about 53 gallons (201 liters). Plan changes from your nitrate reading
How many fish can go in a 125 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 57 | 3 |
| Bronze corydoras | up to 44 | 6 |
| Molly | up to 21 | 3 |
| Tiger barb | up to 40 | 8 |
| Yellow lab | up to 21 | 4 |
| Angelfish | up to 4 | 1 |
| Boeseman's rainbowfish | up to 18 | 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 125 gallon tank?
A standard 125 gallon glass tank is 72 × 18 × 21 inches (183 × 46 × 53 cm), measured on the outside as length × width × height. Brands differ by up to half an inch.
How much does a 125 gallon tank weigh?
Empty, about 140 lb (65 kg). Filled with water, gravel and rocks, about 1,220 lb (555 kg). Add the weight of the stand to find the load on your floor.
What size heater does a 125 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 125 gallon tank?
It depends on the fish, not just the gallons. As the only kind in the tank, a 125 gallon tank carries about 60 or more neon tetras, or 57 guppies, or 44 bronze corydoras. Mixed tanks hold fewer of each.
How many liters is a 125 gallon tank?
125 US gallons is 473 liters. Once set up with gravel and decor, the tank holds about 402 liters (106 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