Keeping Snakes Together

[Zephyr]

Or, alternatively, keep the snakes very well-fed.
I'd think a dekays x garter would be alright, I often find them together in the wild.

[adamanteus]

I'm inclined to agree with Shannon on this one. Whilst it is possible to keep mixed genera/size snakes together, it just isn't safe. You may get away with it for ages and then, one day... disaster!
Best to keep a group/pair of just one genus of similarly sized snakes together.
Also, as Reed said, if you have mixed species of mixed sex together you are likely to get unwanted hybridization.
Personally, I keep all my species/sub-species separate.