Couple Random Questions
Just look for sellers who say they have not mixed their endlers and keep them in a tank without other livebearers. I keep black bar endlers myself. I like them a lot. But there's all kinds like lime green (which I saw on the for sale threads here not too long ago), peacocks, snakeskin and tigers. Picking one of those is a matter of taste.
Again, just make sure the seller clearly states that they are not mixed, either class P or class N. Class N are the purest and can be traced back to Asrian HD, who is the "father" of endlers. Class P's are still top notch,they just can't be traced. If you are interested in black bars, let me know. Depending on my schedule and stuff, I may be able to hook you up.