It is about 5-6" ive had it and a smaller less colorful festivum for almost a year now. The LFS said they came from they came together. The top of his body has been developing a really nice light metallic blue coloring that doesnt look as nice in the pictures.
The one you are asking about looks like a Mesonauta mirificus to me ... but it is a hard genus to ID properly. No clue on the smaller one, pics of it aren't showing enough to check the diagnostics on.