I'm making a mini-eco-system, fertilizer ideas anyone?

Im thinking horse doody in my backyard wont harm the insects, toads, worms, and other small creatures in this gl Bottle ecosystem. The bottle is very large, better than three gallons, maybe more than four. I might forget about putting a toad in there, since theyre used to roaming all around. But im defininetly going to buy some crickets from a petstore that would normally be going straight to their death and give them a new home, LOL. Anyways I am pretty sure that any chemical fertilizer I would use for keeping the gr and other small plants healthy would also kill some of these small insects, also i know i have found worms under piles of horse manure while collecing for makin my compost pile. So I am pretty sure its ok to use around these small insects, in case the gres quit growing or start to wilt. Thanks.. Bye.