Chick Stuff - Advice Anyone?

My little bird seems to be over the ant bites - by Sunday afternoon he was much perkier, and now seems like his old self. I am thankful the Lord sees fit to even care about the 'insignificant' things like hurt little animals. Or maybe it's that He cares about us, and our attachment to them :). At any rate, I'm glad He saw fit to right my mistake (leaving the chick in the yard in the first place). The only problem is, I am now going to have to re-think my 'solution' for the chick's independence. Because of the ants, the cage I was going to use will not work - the ants could crawl right up and over the lower boards. I thought of sprinkling poison around the cage to prevent that, but then the other chickens might get in it (especially the four young ones - they are still pretty dumb Lol). Then I thought, "What about a 'moat'?" you know, like they had around castles in the old days. The ants couldn't get through water. Now, that's all well and good, but where am I going to find a portable moat?! I can't build it - water would seep through wood, plastic would have to be cut, molded, and caulked together (which I wouldn't know how to do) and metal would be the same problem, except that would be even trickier, 'cause it would envolve sautering (spelling-?). Besides, I haven't got alot of money to spend on this whole little situation here. Here is a drawing I did of the idea:



The cage would sit in the hollow space inside.

Does anyone have any advice on how I could build or find something like this? I would really appreciate any tips!