What Is This Fish?

I agree, definitely not forktail rainbows. The body shape and colouring are wrong. {For anyone else reading this, forktail rainbows look like this}


But as to what they are 

Is the photo accurate, is the fish grey with an orange tail and lower back part of its body? I know from taking fish photos hat they often come out looking like a different fish - well, mine do  .

The head and fin shapes don't look quite right for a Melanotaenia species - the only one that fits those colours is a stressed boeseman's rainbow.

I can only think it is a tetra of some sort. Does it have a tiny fin on its back between the main dorsal fin and the tail?

If it has that small fin - an adipose fin - it's a tetra. They are the only aquarium fish that have the adipose fin.

The problem now is which tetra? There are so many of them. Looking at photos of tetras with red tails, they don't have red on their bodies.

Do you know where your friend got them? It might be easiest to make a visit to the shop and see if they still have them. Even if they don't, they may recognise them.

You could have got it there, Extreme 

Have a look at the second photo here


If that's what they are, you'll need more than the three off your friend. The minimum for neon tetras is 6. Though since these tetras are just 'modified' neon tetras, getting 'ordinary' neon tetras would be OK. IF they are indeed gold or diamond neon tetras.

Could this be Rathbun's (a.k.a Redflank) Bloodfin?

See :http://www.seriouslyfish.com/species/aphyocharax-rathbuni/

That does look a possible candidate.

Fin-nipper though, so if it is that species, need to be careful with tank-mate selection.

There are a number of deep bodied tetras ( serpae, phantoms, bleeding hearts etc) but I haven't managed to find any that match the colouring.

Richard W wins !

They really need to be in a group of at least 6
http://www.seriouslyfish.com/species/aphyocharax-rathbuni