Looks to me like it is a male veil tail. Fairly easy to care for but is often mistreated. I wouldnt ever put 1 in a tank less than 2.5g. 5 minimum is a safe bet but a 10g would be better still. Low water flow with mid to high 70s temp is good for it.
"The simplest explanation for some phenomenon is more likely to be accurate than more complicated explanations." -Occam's razor