What fish are best for a tropical nano tank?
The short and rather obtuse answer to this question is shrimps! The many attractive colour forms of domesticated Caridina and Neocaridina shrimp are perfect for tiny tanks that are often too small for fish. In the last few years they've become very popular and a whole range of products from substrates to foods have been developed to make keeping them a simple joy. Species such as Cherry shrimp (Neocaridina davidi var) and Crystal red shrimp (Caridina cantonensis) are gorgeous and fascinating little beasties.
Some fish choices are better than others and male Bettas or Siamese fighting fish (Betta splendens) are often a good choice if temperatures are high and an absolute minimum size of five litres applied. Some tiny shoaling cyprinids loosely grouped as 'Microrasboras' can be a good choice as long as adequate space exists for a shoal and for algae control, Otos (Otocinclus sp.) are ideal and are happiest in groups.
For real fish-lovers, shell-dwelling cichlids are perfect for larger nano tanks and will captivate you with their antics.