Maybe he's thinking of a golden algae eater, Gyrinocheilus aymonieri, which I think is the CAE, but gold form?
Killies prefer softer water, so a subtrate such as aragonite would probably no be a good idea. If you want a darker substrate (this makes the killies colour show quite well), you could look at collecting some fine gravel from Westshore or Marine Parade - not too close to the Fertilizer works, though.
Wash it well, and try to take out as many shells as you can. We usually stick it in a bucket and run the hose in it for a couple of hours, swirling it around occasionally, then put it in the tank.