I know the feeling, I think all Pyrrhulina and Copella spp. are usually labelled as "Copella arnoldi" in shops..<http://www.ukaps.org/forum/threads/splash-tetra-copella-arnoldi.32494/>Copella arnoldi
Your fish could be C. guttata, although I still think it is most likely to be P. brevis or close. You would keep all Copella, Copeina, Pyrrhulina etc the same, as they are pretty closely related.Copeina guttata
Shame, I know a couple of people who breed the true C. arnoldi in the UK.darrel , from asia