What is a 20 gallon long tank good for?
The 20 gallon long holds the same water as the 20 high, spread over a 30 inch footprint. Fish care more about floor and swimming length than height, so many keepers call this the best small tank there is.
How much water does it really hold?
The label says 20 gallons (76 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 20 gallon long tank holds about 17 gallons (64 liters). Use that smaller number when you dose medicine or water conditioner. Work out your exact water volume
How much does a 20 gallon long tank weigh?
An empty glass 20 gallon long tank weighs about 19 lb (9 kg). Filled, with gravel and a few rocks, it weighs about 205 lb (95 kg). That is as much as an adult person, so put it on a sturdy, level surface. The load on the floor under the tank is about 82 lb per square foot (400 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) | 50 W |
| Normal room, 68 °F (20 °C) | 100 W |
| Cold room, 63 °F (17 °C) | 150 W |
Check your own room and target temperature
What size filter does it need?
For a community tank, look for a filter rated at 70–100 GPH (250–400 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) | 20 lb9 kg | 21 lb10 kg |
| 2 in (5 cm) | 39 lb18 kg | 41 lb19 kg |
| 3 in (7.5 cm) | 58 lb27 kg | 62 lb28 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 4.3 gallons (16 liters) for this tank. A big clean-up change is half: about 8.5 gallons (32 liters). Plan changes from your nitrate reading
How many fish can go in a 20 gallon long 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 | up to 16 | 6 |
| Guppy | up to 9 | 3 |
| Harlequin rasbora | up to 12 | 6 |
| Platy | up to 7 | 3 |
| Panda corydoras | up to 11 | 6 |
| Honey gourami | up to 2 | 1 |
| Bronze corydoras | up to 7 | 6 |
| Zebra danio | up to 11 | 6 |
| Cherry barb | up to 11 | 6 |
| German blue ram | 2 | 2 |
Stocking ideas that work
20 long, two schools: 7 harlequin rasboras, 6 panda corydoras. Stocking level 91%. A 20 long has the floor area panda corydoras need. Use sand to protect their barbels.
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 goldfish: grows to 12 in (30 cm) and needs at least 75 gallons (284 liters).
- Oscar: grows to 12 in (30 cm) and needs at least 75 gallons (284 liters).
- 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).
Questions and answers
What are the dimensions of a 20 gallon long tank?
A standard 20 gallon long glass tank is 30 × 12 × 12 inches (76 × 30 × 30 cm), measured on the outside as length × width × height. Brands differ by up to half an inch.
How much does a 20 gallon long tank weigh?
Empty, about 19 lb (9 kg). Filled with water, gravel and rocks, about 205 lb (95 kg). Add the weight of the stand to find the load on your floor.
What size heater does a 20 gallon long tank need?
In a normal room at 68 °F (20 °C), 100 W holds 78 °F (25.5 °C). In a cold room use 150 W; in a warm room 50 W is enough.
How many fish can I put in a 20 gallon long tank?
It depends on the fish, not just the gallons. As the only kind in the tank, a 20 gallon long tank carries about 16 neon tetras, or 9 guppies, or 12 harlequin rasboras. Mixed tanks hold fewer of each.
How many liters is a 20 gallon long tank?
20 US gallons is 76 liters. Once set up with gravel and decor, the tank holds about 64 liters (17 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