I feed a stray cat that lives under my house, before I leave in the morning for work, then again after I get home. Lately, there has been little black ants in the water. I'm not talking about a couple, I mean 20 or 30 or more, every single time I retrieve the dish. I have no idea where they are coming from, but I would really like to get rid of them. How would I be able to do so without harming the stray cat? I'm not able to afford anything expensive, so please keep that in mind when offering your suggestions. Thanks!