Compatibility brief
Can Black ghost knifefish live with Guppy?
Risky. This mix is commonly discouraged for typical setups.
Compatibility score
Profile confidence: low
Order of checkstank volume vs adults → predation mouth gap → temperament / fin nipping → shared water windows.
500L
Combined minimum footprint reference for these two species: about 500L (larger active fish often want more length).
Black ghost knifefish (45cm adult) may treat small Guppy (~5cm) as food once grown — plan adult sizes, not shop sizes.
Black ghost knifefish is a fin nipper and Guppy is vulnerable to nipping — long fins are a common target even when water parameters match.
Assessment details
Temperament difference
Black ghost knifefish is semi-aggressive, while Guppy is peaceful. Expect chasing or stress unless the tank is large and heavily structured — monitor closely.
Black ghost knifefish may eat Guppy
Top issueBlack ghost knifefish (45cm) is predatory and Guppy (5cm) is small enough to be eaten. This pairing is unsafe.
Fin nipping risk
Black ghost knifefish is a known fin nipper and Guppy has long, flowing fins. Black ghost knifefish will likely harass Guppy.
Compatible temperature range
Both fish can comfortably share similar water temperatures.
Narrow pH overlap
These fish can share water but their ideal pH ranges overlap only slightly. Aim to keep pH stable in the shared range.
“Black ghost knifefish (45cm) is predatory and Guppy (5cm) is…”
Black ghost knifefish may eat Guppy
Next steps
Concrete changes, not "research more" filler.
- •Provide plenty of hiding spots and visual breaks so Guppy can escape if harassed.
- •Avoid keeping Black ghost knifefish with long-finned fish like Guppy.
- •Black ghost knifefish reaches ~45cm: tank length and turning room matter more than the litre number. A tall, short tank of the same volume is not equivalent.
Try instead
- →Build a species-only tank for the larger fish, or restock with fish too large to be eaten at adult sizes.
- LiveAquaria. Black ghost knifefish (Apteronotus albifrons care sheet)
Primary: large-aquarium retailer care profile: very large tank, dim lighting, hiding, carnivore diet, and size expectations. Cross-check the stated minimum with your own footprint and filtration; Fishori uses a stricter home-aquarium minimum than a catalog line.
- FishBase. Apteronotus albifrons
Secondary: natural history and max length; weakly electric foraging in the dark. Translate into tank length and nocturnal feeding, not a neon-tetra list.
- Seriously Fish. Poecilia reticulata
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Poecilia reticulata
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Poecilia reticulata
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
- Wikipedia. Guppy
Encyclopaedia overview; use specialist aquarium sources for your stock's real temperature/pH/footprint needs.
Try this next
Build the full stocking list with Black ghost knifefish + Guppy
Plan further
Check each species’ mates list, size the glass, then verify the full stock in the builder. Methodology explains how verdicts are produced.
Individual fish vary in personality. Fishori uses conservative hobby rules. Observe any new introduction closely, feed thoughtfully, and keep a quarantine or backup plan. This is not veterinary advice.
Profile data confidence: medium. Driven by the lower-confidence profile (Black ghost knifefish): Typical care sources — real tanks still vary.