๐Ÿ  Fish Compatibility Guide

Can Black Ghost Knifefish and Black Ruby Barb Live Together?

Updated September 23, 2026 ยท FishCare AI Editorial Team

โŒ Not Compatible โ€” Compatibility Score: 32/100
32/100 โ€” Not Compatible

Black Ghost Knifefish and Black Ruby Barb Compatibility Overview

Black Ghost Knifefish and Black Ruby Barb are generally not recommended to be housed together. The adult size gap creates a meaningful predation risk. Review the behavior and water details before deciding whether to attempt the pairing.

Compatibility factors for Black Ghost Knifefish and Black Ruby Barb
FactorBlack Ghost KnifefishBlack Ruby BarbVerdict
Temperature73โ€“82ยฐF68โ€“81ยฐFโœ… 73โ€“81ยฐF
pH Range6.0โ€“8.05.5โ€“7.5โœ… 6.0โ€“7.5
Temperamentsemipeacefulโš ๏ธ Monitor
Adult Size18.0 in2.2 inโŒ 8ร— difference
Min. Group1+6+See below
Min. Tank Size100 gallons (for both species)โ€”

Compatibility Positives

A stable shared temperature range is available.
Their pH requirements overlap.
Temperament risk is relatively low when normal group sizes are maintained.

Incompatibility Reasons

The adult size gap creates a meaningful predation risk.

Species Profiles

Black Ghost Knifefish โ€” Apteronotus albifrons

Black Ghost Knifefish and Black Ruby Barb compatibility โ€” Black Ghost Knifefish

The Black Ghost Knifefish is a unique and elegant addition to the aquarium. With a lifespan of 5-8 years, it requires a minimum tank size of 200 liters. It is a solitary fish with a low aggression level and moderate activity. Its slender body and silver-blue coloration make it a captivating sight.

โ†’ Full Black Ghost Knifefish care guide

Black Ruby Barb โ€” Pethia nigrofasciata

Black Ghost Knifefish and Black Ruby Barb compatibility โ€” Black Ruby Barb

The Black Ruby Barb is a vibrant, active species suitable for beginners. It requires a spacious tank and a school of its own kind to thrive. Its striking colors and lively nature make it a popular choice.

โ†’ Full Black Ruby Barb care guide

Frequently Asked Questions

Can Black Ghost Knifefish live with Black Ruby Barb?

Generally not recommended. Black Ghost Knifefish and Black Ruby Barb are generally not recommended to be housed together. The adult size gap creates a meaningful predation risk. Review the behavior and water details before deciding whether to attempt the pairing.

What tank size do I need for Black Ghost Knifefish and Black Ruby Barb together?

A minimum of 100 gallons is recommended for keeping Black Ghost Knifefish and Black Ruby Barb together. A larger tank improves water stability and reduces territorial conflict.

What temperature suits both Black Ghost Knifefish and Black Ruby Barb?

73โ€“81ยฐF โ€” inside Black Ghost Knifefish's 73โ€“82ยฐF and Black Ruby Barb's 68โ€“81ยฐF.

Is a Black Ghost Knifefish aggressive toward a Black Ruby Barb?

The adult size gap creates a meaningful predation risk.

Related Compatibility Guides

Tank Size for Black Ghost Knifefish and Black Ruby Barb

Use the scenario that matches the actual group sizes and temperament you plan to keep.

ScenarioTankWhen it applies
Minimum viable100 galOnly for the recommended minimum groups, mature filtration, and close monitoring.
Recommended community150 galAdds territory, swimming room, and a safer buffer for behavior.
Low-conflict setup220 galBest when keeping larger schools or reducing territorial pressure.