Phil, I'm really glad you asked, especially *before* doing it, rather than your post being "Why did my tarantula eat my snake?"

Forgive me if I am wrong, but it seems as if you are new to animal husbandry. There is NOTHING wrong with that, and we all start somewhere. This is a great forum with which to start, I am by no means a zoologist or biologist or any other certified "ologist", myself. I learn something on this and other forums daily, if not more often than that. Even our most experienced keepers on here are constantly learning, just look at the books on "What are you reading" thread, and the abstracts and papers authored or referenced by them. (Genuflecting to those Thamnophis gods now, LOL). Keep reading, keep researching, and keep learning.

Mixed-species enclosure are a growing trend for zoos, aquariums and even some hobbyists. However, it seems to me, a great deal of research and knowledge go into these things, not to mention a huge amount of space and a large budget. The National Aquarium at Baltimore does it very well, I was amazed at their Rainforest exhibit.

If you really want a mixed-species enclosure, what about mixing your garters with some feeder species? For example, you could do your research and create a paludarium: a tank with water and land portions. Create an environment conducive for your garters on the land, and seed the water portions with garter safe fish.

Plant the water portion, and give plenty of cover in which, say, your black dace minnows or guppies could hide and breed, and your garters will be fat and happy, and your feed bill might be negligible. You could make a huge one, and even have some frogs, small ones not a threat to snakes like bullfrogs are, and the frogs eat the fish and frog food, and the garters eat the tadpoles and fish, etc. but the frogs are still viewed as "feeders" rather than pets.

Or put very large but HERBIVOROUS fish that would pose no threat to the garters in the water enclosure, I would say fish so large that there is NO WAY the snakes would try to eat them. I would say that whatever you chose to put in there, make sure your garters are at the top of the food chain. Don't get attached to a "favorite Minnow named Fred". Be prepared to restock your feeder pond as needed. And lastly, the paludarium would give your garter babies a great place to swim.

Just out of curiosity, what inspired you to want a mixed-species enclosure in the first place?

I myself would love to create a paludarium worthy of Princess Ernestine and King James. Right now, it's not a possibility, so they have fake plants, and laticrete hide rocks.