What can I keep with this bossy fish?

Serpae tetras are stunning, but renowned for fin-nipping behaviour.

I have just got into fishkeeping and I have a 40 l/11 gal tropical tank that currently has two Serpae tetra in it. I was wondering what tank mates I could add as everything I have read about them has told me they are quite dominant. I would like some colourful mid to top dwellers if possible.
DANIEL FAIRLIE, EMAIL

Serpae tetra, Hyphessobrycon eques, do indeed have a somewhat deserved reputation as pugnacious, ‘nippy’ fish and will often dominate and bully less robust species. The best way to lessen the chances of this occurring is to stock them in larger numbers; I would recommend a bare minimum of ten but even then they may still be a problem with some fish. Unfortunately, your tank is too small for this as these active fish can reach 4cm/1.6in long. 

Ember tetra,  Hyphessobrycon amandae.

My recommendation would be to return your two existing fish to the shop you bought them from, and replace them with a group of at least six Ember tetra, Hyphessobrycon amandae, which share similar burnt orange colouration, but typically grow about half the size and are not aggressive like the Serpaes. 

Adding some hardy live plants such as Cryptocoryne and Anubias will provide more cover and bring out better colour in your fish, and then perhaps you could consider a few Sparkling gourami, Trichopsis pumila, to fill the upper layers (add some floating plants if you do) and maybe a group of five Kuhli loach, Pangio semicincta, for the bottom.  
BOB MEHEN