Orange spotted goby sex

[Moort82]

As far as I can remember there isn't a reliable way to differentiate between the sexes of these gobies but does anyone know if they have determined sexes?
I have a resident OSG and I'd like to try and pair it. Its still a baby at 2" or so and have seen a decent one of a similar size which I wouldn't mind trying it with. Just wondered if anyone else has tried anything similar?

TIA

 

[Moort82]

Perhaps should have said I was meaning Amblyeleotris guttata as opposed to the Valenciennea sp often called the same name.

I have just spotted that mine currently has a normal dorsal fin whereas a lot of those I see have extended fin rays. Does anyone know if this is a sign of maturity? or it might be a gender difference? the one I was considering trying with mine is the same size but sporting these extensions.