Aquario — Your Trusted Guide to the World of Aquarium Fish

Dreaming of creating the perfect aquarium but don't know where to start? Looking for new inhabitants for your underwater world? Aquario is your personal assistant in the world of aquaristics!

Fishes Compare

What's inside

The sections are linked: from a species card you can see who it will live with, which plants it will leave alone and how much water it needs.

1249 species

Aquarium fish catalogue

Every species lists tank volume, temperature, pH and hardness, adult size, temperament, diet and lifespan. The filter works on those same fields: describe your tank and see who will be comfortable in it.

Open the catalogue 277 species

Aquarium plants

Light, substrate, CO₂, growth rate and where the plant belongs — foreground or background. Each one notes which fish will eat it or dig it up.

Browse plants 510 species in the matrix

Aquarium fish compatibility

Three verdicts per pair — compatible, with care, not recommended — each with its reason. Pick one fish and get the whole list of its tank mates.

Check a pair Volume and equipment

Tank calculator

Works out volume from length, width and height with an allowance for substrate, suggests a heater and a filter, and checks whether the stocking you have in mind will fit.

Open the calculator Natural ranges

Range map

Where a species lives in the wild, plotted on the world map. Useful for understanding the water it is used to.

Open the map 9 guides

Aquarium articles

Starting a tank and the nitrogen cycle, water chemistry, diseases, feeding, breeding, nano tanks, and an algae key that works by appearance.

Read the articles Up to four species side by side

Species comparison

Puts cards next to each other and shows where species differ: volume, water, temperament. Plants compare the same way.

Compare species

What is known about every species

A shoaling species, a pair or a loner — and how many individuals it takes for the fish to behave calmly. Volume is given for that group, not for one fish.

What to feed and how often, whether it needs plant matter, and what does not suit this species.

Jumping, danger to smaller tank mates, demands on flow and substrate — the things you find out late and expensively.

How the species breeds, what spawning takes, and how long it lives under decent care.

Where to start with an aquarium

Settle the volume
If you already have a tank, measure it. If not, the calculator works it out from the dimensions. This alone rules out half the catalogue.
Open the calculator
Pick the residents
Enter your volume, temperature and water hardness in the filter — the catalogue keeps only the species they suit.
Open the catalogue
Check they will get along
The matrix shows pair by pair who will eat or harass whom. Cheaper to learn here than in the tank.
Check a pair

Common questions

How many fish fit in a 20-litre tank?

It depends on the species, not on the number. 15 species in the catalogue are fine in twenty litres; the rest need more. And the volume on a card is given for a group the species lives in properly, not for a single fish.

Which aquarium fish are the easiest to keep?

The catalogue has a separate beginner category — 39 species reckoned the most forgiving of a newcomer’s mistakes. That does not mean no preparation is needed: they still have their own volume, temperature and tank mates.

Which aquarium fish get along together?

It is settled pair by pair, not by a list of peaceful species. The compatibility matrix covers 510 species and gives every pair one of three verdicts — compatible, with care, not recommended — along with the reason. Most often the trouble is a difference in size, temperament or water requirements.

How do you work out aquarium volume?

From the internal dimensions: length × width × height, less the substrate. The calculator does it for you and also suggests heater wattage and filter throughput.

What has to be done before adding fish?

Let the tank settle with the filter running. The bacteria that process ammonia do not appear at once — it usually takes a few weeks. There is a separate article on the nitrogen cycle.

The catalogue is built so that the numbers can be acted on. Volume is given for a group the species is comfortable in, not for a single fish; temperature and pH are working values, not the extremes a fish will survive.

Where there was no certainty, the card carries a caveat rather than an averaged number. Better to say nothing than to say something that costs a fish its life.

The sections lead into one another: from a fish card you can move to its tank mates, to the plants it will not touch, and to the article on what to feed it. That is what a handbook is for — not a list of species, but answers to the questions in the order they come up.