Swordtail and Discus: Can They Live Together?
Side-by-side comparison
| Factor | Swordtail | Discus | Assessment |
|---|---|---|---|
| Water temperature | 72–82°F | 82–88°F | Narrow overlap |
| pH | 7–8.4 | 5.5–7 | Tight overlap |
| Hardness | 12–30 dGH | 1–8 dGH | No overlap |
| Adult size | 5.5″ | 8.0″ | Similar |
| Temperament | Peaceful | Peaceful | Both peaceful |
| Swim level | Mid | Mid | Same zone |
| Minimum tank | 20 gal | 55 gal | Together: 55 gal+ |
Shared water parameters
- Temperature both tolerate: 82–82°F
- pH both tolerate: 7–7
- No shared hardness window.
- Recommended combined tank: 55 gallons or larger
Risks and things to watch
Temperature conflict
The comfortable ranges barely meet. Running one species at the edge of its range for months is a slow-burn health problem, not an instant one — which is why it often goes unnoticed.
Both occupy the mid zone
Competition for space and food is higher when two species share the same layer. Increase footprint rather than height.
Group requirements
Compatibility is not only about the two species getting along — each still needs its own social setup met inside the same tank.
- Swordtail — minimum group of 3. Budget tank space for the whole shoal, not one fish.
- Discus — minimum group of 5. Budget tank space for the whole shoal, not one fish.
Frequently asked questions
Can swordtail and discus live together?
Yes — compatible. Swordtail and Discus are a good match. They share a workable temperature and pH window, neither is large enough to threaten the other, and temperaments are compatible. Give them at least 55 gallons once both group requirements are met.
What size tank do swordtail and discus need together?
Plan for at least 55 gallons. Swordtail alone needs 20 gallons and Discus needs 55, but combined stocking needs headroom for filtration and swimming space, not just volume.
What temperature suits both species?
Both are comfortable between 82 and 82°F. Set the heater to the middle of that window and keep it stable.
What pH works for both?
Aim for pH 7–7, which sits inside both species' comfortable range.
Will discus eat swordtail?
Unlikely. At 8.0″ versus 5.5″ the size gap is not large enough for predation, though fry and juveniles are never safe in a community tank.
How should the tank be arranged?
Use plants, wood and rock to break sight lines, keep open swimming space along the front, and add the more territorial species last so it cannot claim the whole tank before the other settles in.
Explore further
Assessment generated from our compatibility methodology: parameter overlap, adult size ratio, temperament and swimming zone. Reviewed by Marcus Rivera.