What Size Tank Does a Discus Need?
Adult standard length 6 inches, and they grow as tall as they are long. About 48 × 18 × 18 inches (255 liters) for a few juveniles or a breeding pair.
Full breakdown: how many fish per gallon.
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The figures
| Figure | Value | Source |
|---|---|---|
| Adult standard length | 6 in | Seriously Fish |
| Minimum aquarium | about 48 × 18 × 18 in | Seriously Fish |
| Published volume | 255 liters, for a few juveniles or a breeding pair | Seriously Fish |
| Volume converted to US gallons | 67.37 US gallons (255 ÷ 3.785) | Calculated from the published liters ÷ 3.785 (Seriously Fish; 1 US gallon = 3.785 liters) |
| Rounded shopping size | 67 US gallons (67.37 rounded to the nearest gallon) | Calculated from the published liters ÷ 3.785 (Seriously Fish; 1 US gallon = 3.785 liters) |
| Proportions | Grow as tall as they are long | Seriously Fish |
| Filter rating | Not listed | Seriously Fish |
| Heater on the profile | Not listed | Seriously Fish |
| Aqueon bands that contain 67.37 gallons | 200 watts for 50-75 gallons, and 300 watts for 65-90 gallons | Aqueon |
How to size it
Height is the sentence next to the tank, not a flourish. Seriously Fish gives about 48 × 18 × 18 inches (255 liters) for a few juveniles or a breeding pair, and says the fish grow as tall as they are long. Adult standard length is 6 inches, the same length printed for angelfish, on a different tank: the angelfish minimum is 39 × 16 × 20 inches and about 53 US gallons. Discus volume is published in liters.
The shopping link searches a 67 gallon aquarium, that rounded gallon, not a claim that the profile printed 67. The 18 inch height matches the 18 inch width, which is the published way of saying the fish need a tall box. No headcount beyond "a few juveniles or a breeding pair" is printed, so none is added.
Filter liters and heater watts are not listed, so none are calculated from the four-to-five turnover rule. The heater figure that is available is the volume chart. Aqueon includes 67.37 in the 200 watt band because 67.37 is between 50 and 75, and in the 300 watt band because 67.37 is between 65 and 90. It is outside the 150 watt band, which ends at 55. A 55 gallon tank is short of 67.37; a 75 gallon tank contains it, because 67.37 is not above 75.
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No species heater wattage is listed. The second product is the lower overlapping Aqueon band (200 watts for 50-75 gallons). Accessory: a thermometer, because the profile does not list a temperature in the figures used here. Shop a digital aquarium thermometer on Amazon
Related pages
- Stocking calculator
- What size tank an angelfish needs
- What size tank an oscar needs
- What size heater a 75 gallon tank needs
FAQ
What size tank does a discus need?
Seriously Fish lists about 48 × 18 × 18 inches (255 liters) for Symphysodon aequifasciatus, for a few juveniles or a breeding pair, and says they grow as tall as they are long. 255 divided by 3.785 is 67.37 US gallons. Adult standard length is 6 inches.
What filter and heater wattage does the discus profile list?
No filter rating and no heater wattage are listed for this profile. Aqueon's 200 watt band is 50-75 gallons, and the 300 watt band is 65-90 gallons. 67.37 gallons sits in both.
Does a 55 gallon tank meet the discus minimum?
No. The converted volume is 67.37 US gallons, which is above 55. It is inside Aqueon's 50-75 gallon band for 200 watts and inside the 65-90 gallon band for 300 watts.
Why does the shopping link say 67 gallons?
255 liters converts to 67.37 US gallons, and 67.37 rounds to 67 gallons. The published volume remains 255 liters.
Sources
- Seriously Fish, Symphysodon aequifasciatus. https://www.seriouslyfish.com/species/symphysodon-aequifasciatus/. Accessed Oct 2, 2026.
- Aqueon, Heater Wattage Guidelines. https://www.aqueon.com/-/media/project/oneweb/aqueon/files/us/educational/aq_heater_wattage_chart.pdf. Accessed Oct 2, 2026.