I don't know if you can make a bonsai out of them but Calamondin is often grafted on dwarfing C. trifoliata 'Flying Dragon' rootstock (at least over here in Europe) which helps in keeping control of the tree size.
Nik

For a very dwarf citrus plant you can try to get hold of a small leaved C. myrtifolia 'Chinotto' which is very small by design.
Nik

This is how the tree looks, i was wondering if I should cut back the new branches? Would that hurt the tree or should i cut it back?

Nik, i dont think this tree needs to be grafted, or does it? haha im new to citrus trees:)

From the picture it looks grafted to me. Can't be sure though. Most citrus is grafted and calamondin sure comes grafted here in Europe.
Nik

Yes, I think the tree is grafted, because I live in europe too, norway. But do you think I should cut back the branches?

I know nothing about bonzai so I can't help you on that. If this plant were to grow normally I would not cut off the shoots.
PS I 'm wondering if citrus can live with the level of light in a Norwegian living room in winter.
Nik

This post was edited by nikthegreek on Tue, Apr 29, 14 at 12:22

If it's anything like the one I bought just let it grow. It'll look a bit messy for a while but it will sort itself out.

Mine was grafted, thought I've no idea what what rootstock it's on.

Regards
Nick