'Nano' aquariums: Nice idea, just not for the fish

If you have a small flat but still want to keep fish, or your child wants some in their bedroom, a so-called "nano aquarium" might seem like the right way to go.

These smaller-sized aquariums are increasingly available online and in pet shops - and yet they are entirely inappropriate for many sea creatures in the long term, according to Germany's Association for Professional Nature, Animal and Species Conservation (BNA) points out.

Nano aquariums often have an edge length of 30 to 50 centimetres and a capacity far less than 54 litres. However ornamental fish should be kept permanently in a tank with a capacity of at least 54 litres, preferably more, according to the BNA. This corresponds roughly to an aquarium measuring 60 by 30 centimetres.

But are nano aquariums still useful? Yes, nano aquariums can be suitable for keeping small invertebrates, such as freshwater and seawater shrimps, or even just aquatic plants, the conservation experts say. The association recommends cherry shrimp (Neocaridina davidi), for example.

If you want to keep ornamental fish in a slightly larger aquarium, you'll need to keep their numbers in check. A maximum of two to three species per tank is usually the ideal number for the welfare of the animals - and the characters of the respective fish species should work well together.

Fish in slightly larger small aquariums also need to be fed sparingly - enough so that they don't starve, but also not in such quantities that too many nutrients pass into the water and the water parameters are no longer in balance.

The BNA recommends changing around 30 to 50% of the water every week and removing some of the sludge and dead plant debris. In addition you should check the filter regularly and clean it if needed.