This is a fun tetra taken in one of my quarantine tanks. It's entered the hobby as Hyphessobrycon sp Red Cherry, or Cherry Red. It's a small, undescribed species from the Amazon region.
There are lot of red tetras, but the specific red of this one is very nice, and the yellow females are striking as well. They look like two different fish. I have one I bought as female showing a lot of incoming male colouration in the QT tank.
I have them at 23c, in 65 tds water tinted by tannins. For the QT period, they are sharing with Congochromis sabinae - some very young, unsexable Congolese dwarf Cichlids. It's early days, but I like this one.