Compatibility Overview
Swordtail and Watchman Goby are generally not recommended to be housed together. The issues listed above — whether water parameter incompatibility, predation risk, or aggression — create conditions where one or both fish are likely to suffer harm or chronic stress.
| Factor | Swordtail | Watchman Goby | Verdict |
|---|---|---|---|
| Temperature | 65–80°F | 72–82°F | ✅ 72–80°F |
| pH Range | 7.0–8.3 | 8.0–8.3 | ⚠️ 8.0–8.3 (narrow) |
| Temperament | peaceful | semi | ⚠️ Monitor |
| Adult Size | 5 in | 1.2 in | ❌ 4× difference |
| Min. Group | 3+ | 1+ | See below |
| Min. Tank Size | 55 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Swordtail — Xiphophorus hellerii
Hardy livebearer with a distinctive elongated lower tail fin in males. Peaceful community fish that tolerate a wide temperature range.
Watchman Goby — Aquarium species
The Watchman Goby is a peaceful and colorful addition to the marine aquarium. It is known for its slender body and distinctive yellow and dark spot pattern. These gobies are often found in pairs or small groups and require a well-maintained saltwater tank with plenty of hiding spots. With proper care, they can thrive for several years.
Frequently Asked Questions
Can Swordtail live with Watchman Goby?
Generally not recommended. Swordtail and Watchman Goby are generally not recommended to be housed together. The issues listed above — whether water parameter incompatibility, predation risk, or aggression — create conditions where one or both fish are likely to suffer harm or chronic stress.
What tank size do I need for Swordtail and Watchman Goby together?
A minimum of 55 gallons is recommended for keeping Swordtail and Watchman Goby together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Swordtail and Watchman Goby?
72–80°F
Is a Swordtail aggressive toward a Watchman Goby?
Swordtail is peaceful and Watchman Goby is semi. These animals require different water types and cannot share one aquarium.
Related Compatibility Guides
Compatibility score breakdown
The overall score is weighted across water chemistry, behavior, adult size, swimming zone, and social needs. A score is a planning aid—not a guarantee for individual fish.
| Factor | Score |
|---|---|
| Temperature | 80/100 |
| Ph | 100/100 |
| Temperament | 75/100 |
| Adult Size | 38/100 |
| Swim Zone | 92/100 |
| Social Needs | 92/100 |
Tank size scenarios
Use the scenario that matches the actual group sizes and temperament you plan to keep.
| Scenario | Tank | When it applies |
|---|---|---|
| Minimum viable | 55 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 75 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 125 gal | Best when keeping larger schools or reducing territorial pressure. |