New: do these species go together?

The question that comes back most often when stocking a tank is not about one species but about the combination: can this fish live with that shrimp, and will that coral put up with its neighbour? On the new compatibility page you put the species you have in mind on a list and get a verdict per combination.

How it works

You search species by name and add them to your list. Below it a matrix appears: every species sits in a row and in a column, and every cell is one combination. Green means no known objection, amber means the combination asks something of you, and red means the catalog says it does not work. Tap a cell and you read why.

• Water and values. Fresh next to salt drops out right away, and the temperature and pH bands have to overlap.
• Known conflicts. The catalog records per species which relatives and neighbours are better kept out of the same tank; that list is checked in both directions.
• Size and temperament. A carnivore three times the length of its neighbour, an aggressive species next to a peaceful one, a shrimp eater next to shrimp.
• Reef and plants. Species that are not reef safe get a warning as soon as a coral or anemone is on the list; the same goes for plant eaters next to plants.

Above the matrix sits what the list asks for as a whole: the temperature and pH band that fits every species on it, the largest minimum tank volume on the list and the highest care level. Below the matrix the findings appear as plain sentences, along with the per-species points: that a schooling fish wants to be at least eight, for instance, or that a species is on the European list of invasive alien species.

What it is not

The verdicts come from the same catalog as the species database and go no further than what is in it. They take no account of how your tank is laid out, of the character of an individual animal, or of the order in which you introduce the inhabitants. All three help decide how it turns out in practice.

A green cell means the catalog knows of no objection to that combination. That is something other than a guarantee that it will go well.

Where your list stays

The calculating happens in your browser and your list is kept there too, so it is still there next time. No account is needed and nothing goes to a server. If you want to show a list to someone, the species travel in the URL: copy the link and the reader sees the same matrix. Since the site went live this is the first feature that lets you enter something yourself.