Joshua,
Adult size:
Males 2" (5cm) Females 1.5" (4cm)
Males will have a orange/red edging to the tip of the dorsal fin.
females dorsal edging will be much paler, often white.
The female will have much more lavender coloring to her flanks then the male, but the soft rays of her anal fin will be lacking in color to where the males will have color.
The pics you provided are suspect at best, but if I was to venture a guess going from them, I would have to say it's two (2) males.
Although the pH of Lake Tanganyika has been measured in places to be 9.0, it is not necessary to maintain the pH of your aquarium at this. In fact, unless your tap water is 9.0 (unlikely) I would acclimate them to what your normal water values are.
I have bred these successfully in a pH of 7.2 and 7.8 and they thrived!!
It does way more harm than good to "adjust" the pH to attain the lake's parameters.
The only instance I would adjust the aquarium pH is if these are wild caught straight from Lake Tanganyika or they are currently being maintained in a pH higher than 8.0!!
Hope this helps give you some guidelines to judge the two fish you are contemplating getting.
