Try Terro Ant Baits. Put them where the ants can reach them, but the tortoise can't. They are relatively non-toxic. Just boric acid and sugar water, but the tortoise will knock them around and spill them. These work very well in dry areas like ours because the ants go for the water as much as the sugar. Let the ants swarm the air stations and carry the stuff back to the rest of the colony. You can buy these at Home Depot in 6 packs for a few bucks.
That might just work in Arizona.Food grade Diatomaceous Earth works and is tort safe.
That is very trueI have noticed cleaning up old food helps to minimize how much bugs there are. It is more preventative. Sorry I don't have much to offer as far as current ant problems