A planning tool for tropical aquariums.

What this is

A structured database of 136 freshwater species plus a compatibility engine that gives you a verdict on any pair. We score adult size, mouth gap, temperament, fin nipping, schooling needs, and shared water windows. Every result explains itself. There is no black-box rating.

The same checks drive a tank builder for a whole stocking list, not just two fish at a time, and a browseable fish library with cited sources, minimum tank sizes, and the species we’d steer beginners away from.

How we decide

Conservatively. Where two sources disagree, we take the harder number. Where a pair works for experienced keepers but fails for beginners, we flag caution and explain why. A betta with neons can work, but most of the time it doesn’t, so we say so.

The full logic is documented in methodology, including a worked example.

What we don’t claim

We have not personally kept all 136 species. We have read about all of them against multiple sources. Where our confidence is lower, the fish page says so plainly. Where we’ve cross-checked enough sources that the numbers agree across them, the page is marked higher confidence. We don’t hide either label.

We also don’t pretend to model your individual filter, your tap water, your work schedule, or the actual temperament of the actual fish in the actual bag. The verdict is a planning floor, not a guarantee.

The full list of things we don’t do is on the limitations page.

What you should do

Treat any verdict as the first half of a conversation. Read the reasoning. Cross-check water parameters against your tap water (most UK tap water sits in the 7.2–7.8 pH range with medium hardness; most US tap water varies wildly by region). Talk to your local fish shop if it’s a good one, ignore them if it isn’t.

If we’ve got something wrong, tell us at hello@fishori.com. We update profiles, change verdicts, and admit corrections on the methodology page. We don’t crowdsource verdicts in real time, but we do read every email.

Photos, sources, legal

Species photos come from Wikimedia Commons under free licences (CC BY, CC BY-SA). Each file keeps its original licence and credit; full photo credits here. For data sources see source transparency, and for the legal small print see the disclaimer.