The best black sand I have found and am using is this one:
It is not cheap thou, I am looking too for some other dark sand for a 55 gal..
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=7324&N=2004+113555
It is light weight, and seems to stay in place good if you dont' have a lot of water movement.. I like the way it looks..
On your auratus, 3"+ before they start to turn, unsure if you can sex them before. The males wil chase the females more, females do tend to hide from the males...This could help if you just watch how they act around one another..MORE in the tank wil make the male change colors faster to get the females...Pics? I can hunt some down if you really need them..
My 29 gal tank.. it is now full of Dolphin fry so it does not look like this..1 20# bag in this tank..
