Your First Aquarium

First Aquarium - choosing the right fish

The task of choosing your fish

Anyone who has fulfilled the lifelong dream of buying an aquarium will be eager to populate it as quickly as possible! It is important to select the appropriate number of fish for the space you have available, and you will need to ensure you have matched these fish according to their respective needs, such as water type. To do this you should consult a marine expert or other trusted form of guidance.

To give you an idea of the fish you could soon be welcoming into your aquarium, here is an overview of the best-known fish families and an example member of each group:

Live-bearing tooth carps:

The guppy (Poecilia reticulata), also known as the millionfish or rainbow fish, is relatively easy to keep in a range of different water types (excluding the high-breeding guppy) with an ideal temperature of 18-28°C and hardness of dGH 5-25, although it will multiply rapidly. The parents will provide for their young, but in a tank rich in plants there will always be young that hide away. Due to their striking fins, these fish should not be mixed with those that are prone to fin-plucking, including Sumatra barbel or fighting fish.

Labyrinth fish

Siamese fighting fish (Betta splendens) are immediately noticeable thanks to their remarkably beautiful fins, particularly the males. The males can be aggressive amongst one another, so you should always socialise a single male with a number of females. As with all labyrinth fish, Siamese fighting fish breathe atmospheric air, so should not be kept in particularly deep tanks. With proper care, you can watch how the male builds a foam nest and cares for its brood. The ideal temperature is 24-30°C and water hardness is dGH 25.


The harlequin rasbora (Rasbora heteromorpha) is a schooling fish of around 2.5-3.5 cm long, lively and amicable. It should not be kept together with large swarm fish and likes an ideal water temperature of 22-25°C and a hardness of up to dGH 12.


The Bushymouth catfish (Ancistrus dolichopterus) eats algae and is usually the first to move into a new aquarium. The males have fleshy nose bristles that resemble antlers. These fish are generally peaceful and require roots or wood to help their digestion. The males are approximately 12cm long, with the females being slightly smaller, and they thrive in water temperatures of 23-27°C and water hardness of dGH 2-30.


The Ram cichlid (Microgeophagus ramirezi) is a peaceful South-American cichlid reaching up to 5cm long. This breed forms strong relationships and should always be kept in pairs. They prefer water between 22-26°C and with a hardness of up to dGH 10.


The Cardinal tetra (Paracheirodon axelrodi) is a peaceful yet lively schooling fish, measuring up to 5cm and thriving in water temperatures of 23-27°C and hardness of up to dGH 10. These fish look particularly nice against more darkly furnished aquariums.

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Tapping on the Aquarium

Two researchers carried out an investigation into the noise exposure of one of the aquariums due to the visitors in the Schönbrunn Zoo in Vienna, and found some surprising results. They hid an underwater microphone in a one cubic metre aquarium to register the effects of visitors tapping on the glass. Helmut Kractochvil and Harald Schwammer investigated this activity for four weeks, counting the taps per 100 visitors between midday on Monday to midday on Friday, and then from midday to Friday to midday on Monday. They then introduced three different signs with the inscriptions: “Tapping on the glass kills the fish”, “Only idiots tap the glass”, and “Please do not tap the glass”.