Calci-sand is bad for your leos health and is also insanely expensive and a big rip-off. If you really want sand buy washed, screened, fine particle play sand from home depot, it costs about 3$ for a 50lb bag. Although there are many safer substrates (reptile carpet, paper towels, newspaper, shelf liner, linolium, tile etc..).
As far as puting them together never mix babies with adults, all of your leos should be the same size before you put them together. You also want to make sure they are old enough to sex so you dont put two males together. And remember, before adding any leo's to an exsisting collection you need to quarantine them for at least 60-90days in a seperate enclosure.
-----
0.1 Bearded dragon
0.1 mexican kingsnake
1.0.2 Leopard Gecko's
0.0.1 Rose Hair Tarantula
1.0 BTS
0.0.1 Reverse Okeetee Corn
0.1 Bullmastiff
4.1 Cats