Quick intro, I'm Ken from England and very new to the hobby having bought my first shrimp only 3 days ago for my 25g tank, I bought 5 amano shrimp as they seem to be the only kind sold anywhere near where I live. But here's where I need some help, when I got them home I found out that I actually had 6, 5 amano and 1 tiny uninvited guest which despite many hours of searching the net I have not yet been able to identify. The closest likeness I have been able to find is this.

It's almost the same as the above but it's black not red and it has turquoise spots. About the only thing I do know about it is I'm obviously caring for it correctly as it's almost doubled in size already
Any help identifying this would be great, then I can start reading up on it.
Ken