housing different species

Question
I have a loepard gecko around 5 inches and a collared lizard the same size, i have a 30 gallon tank with heat lamp and uvb light. I let them play together for a bit and keep an eye on them. Both seem to think the other is non existant, i have them in seperate cages now except play time. I would like to eventually put both together at sum point if its possible to

Thnx

Answer
No, this is a bad idea, and they should not be placed together.  As you have noted, reptiles do not play, and they do NOT enjoy one another's company.  It is merely stressful for them.  Eventually, they will become annoyed, or compete over food, and someone's going to lose a tail or get a laceration.  It is NOT in your animals' best interests for you to house them together.  Also, end 'play time'.  It's not fun for them at all.  It's stressful.  They feel anxious, not happy.  Reptiles can come to tolerate handling, but it is tolerance, not enjoyment.

They come from different parts of the world, and may carry bacteria or parasites that could make the other sick.  

Additionally, collared lizards require a 115F basking spot!  That is hot--TOO hot for a leopard gecko, which only requires a 90F basking spot.  Collared lizards also require high UVB light, which may irritate the eyes of the nocturnal leopard gecko.  Leoaprd geckos, being nocturnal, should be provided heat using an undertank heat mat controlled by a thermostat.  Collared lizards do better with an overhead basking lamp.  Given their different environmental requirements, I am not sure why you would ever have considered housing them together.  (Assuming you knew their requirements).

You have them housed separately now, and there is no reason not to keep it that way.