Compatibility Report
GuideMyTank compatibility analysis for Black Ghost Knifefish and Congo Tetra.
Planning verdict
incompatibleDo not plan a shared aquarium for this pair. Choose a different tank mate or maintain separate aquariums.
Black Ghost Knifefish and Congo Tetra receive a not recommended verdict from the current structured assessment. Black Ghost Knifefish is recorded as semi-aggressive with an aggression level of 4/10; Congo Tetra is recorded as peaceful with an aggression level of 1/10. The recommendation is based on the combined water, space, behavior, grouping, and predation checks below rather than on species names alone.
Black Ghost Knifefish has a recorded temperature range of 73–82°F and pH range of 6–7.5. Congo Tetra is recorded at 75–82°F and pH 6–7.5. Their shared planning window is 75–82°F for temperature and 6–7.5 for pH. A shared aquarium must stay inside the overlap rather than merely touching each species’ outer tolerance.
Black Ghost Knifefish sets the larger listed base aquarium requirement at 90 gallons; the other listed minimum is 40 gallons. Black Ghost Knifefish is the larger adult by the recorded maximum, reaching 20 inches, compared with 3.5 inches. These figures are starting constraints, not a stocking-capacity calculation, because the complete group sizes and bioload still matter.
Black Ghost Knifefish is a moderate species associated with the cave zone and moderate flow. Congo Tetra is active, uses the mid zone, and has a moderate flow preference. Black Ghost Knifefish does not have a recorded minimum school larger than one, while congo tetra should be planned as a group of at least 6. The aquarium must support both social structures without forcing either species into insufficient space.
Black Ghost Knifefish is recorded as a carnivore with advanced care, while Congo Tetra is a omnivore with intermediate care. Their listed preferred tank styles are blackwater and planted. Feeding access, cover, open swimming room, filtration, and observation should be planned around the more demanding requirement rather than averaged between the two species.
Use these pair-specific boundaries before treating the verdict as an acceptable stocking plan.
Do not plan a shared aquarium for this pair. Choose a different tank mate or maintain separate aquariums.
These references support the underlying species records used by this assessment. They do not necessarily evaluate this exact pair together.
Continue with the most relevant care and compatibility resources for Black Ghost Knifefish and Congo Tetra.