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Compatibility

Compatibility brief

Can Jack Dempsey live with Molly?

Jack Dempsey

Jack Dempsey

Rocio octofasciata

aggressive~25cm
Molly

Molly

Poecilia sphenops

peaceful~10cm
VerdictRISKY

Risky. This mix is commonly discouraged for typical setups.

Jack Dempsey + Molly: Aggression mismatch. Jack Dempsey is aggressive, while Molly is peaceful. The aggressive fish will likely bully or harm the peaceful one. Real tanks add variables Fishori cannot model; treat this as a high-risk read, not certainty.

Compatibility score

30/100

Profile confidence: medium

Order of checkstank volume vs adults → predation mouth gap → temperament / fin nipping → shared water windows.

Min tank

200L

Combined minimum footprint reference for these two species: about 200L (larger active fish often want more length).

Temperature
Range in °C24–28°C shared
Jack DempseyMollyShared window
pH
Range7.5–8 shared
Jack DempseyMollyShared window
Size / predation

Jack Dempsey (25cm adult) may treat small Molly (~10cm) as food once grown — plan adult sizes, not shop sizes.

Temperament / behaviour

Jack Dempsey (aggressive) and Molly (peaceful) are far apart on aggression — bullying or injury is a common outcome in average community layouts.

Assessment details

  1. Aggression mismatch

    Top issue

    Jack Dempsey is aggressive, while Molly is peaceful. The aggressive fish will likely bully or harm the peaceful one.

  2. Jack Dempsey may eat Molly

    Jack Dempsey (25cm) is predatory and Molly (10cm) is small enough to be eaten. This pairing is unsafe.

  3. Compatible temperature range

    Both fish can comfortably share similar water temperatures.

“Jack Dempsey is aggressive, while Molly is peaceful”

Aggression mismatch

Next steps

Concrete changes, not "research more" filler.

Try instead

  • →Build a species-only tank for the larger fish, or restock with fish too large to be eaten at adult sizes.
Sources from both profiles
Only URLs that exist on the species records are shown. We do not fabricate citations.

Try this next

Build the full stocking list with Jack Dempsey + Molly

Compare another pairOpen tank builder

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: high. Checked against several solid care sources that mostly agree.

Full tank-mate guides

Related pair checks

Other tank mates for Jack Dempsey

Jack Dempsey + Molly — common questions

Can Jack Dempsey live with Molly?
For most keepers, no. The verdict is RISKY: at least one check fails hard for a typical home tank. Choose a different pairing, or read the assessment details on this page to see exactly what fails before deciding.
What tank size do you need for Jack Dempsey and Molly together?
Plan around 200 litres as the working minimum. That figure comes from each species' published minimum and their group needs, and it assumes adult sizes, not shop sizes.
What's the main risk?
Aggression mismatch. That is the check that fails outright for this pair. The matching entry under assessment details on this page explains the reasoning and the numbers behind it.