Fish Compatibility Checker

Check whether your picks can actually share a tank. Every verdict traces back to published temperature, pH and hardness ranges, adult size and temperament — and where that data is missing, it says so rather than guessing.

Pick your fish

Add two or more species to compare them against each other.

How to read the result

✓
Compatible — parameters overlap, no size or temperament conflict found.
!
Caution — workable, but something needs managing. The detail notes say what.
×
Not compatible — a concrete conflict, such as no shared temperature range or a genuine predation risk.
?
Can’t assess — the data needed isn’t recorded for one of the species. Not the same as a pass.

Compatibility

Add at least two species to see how they get on.

Where the limits are

Temperature is treated as a hard constraint — fish that can’t share a temperature can’t share a tank. pH and hardness are treated as softer, since most stock adapts within reason.

Individual temperament varies more than any chart admits. A tool narrows the field; it doesn’t replace quarantine, a backup plan, and watching the tank for the first fortnight.

Next step

Once you know they get along, work out how much water they need.

Tank Size Calculator →

Keep track of it

Log the stock you settle on and the journal tracks the tank from there — including whether it has genuinely cycled before you buy anything.

Start a free Tank Journal →