unsuitable habitat?

[mooky]

I have a small pond that is just entering its second year. It is getting well established. I was suprised today to find a fish in it. I didn't put it there! I think I have identified it as a Stone Loach. It has barbels and a silver tummy. When we had some flooding a few weeks ago, I took some mud from the nearby river. Boutonne 79. It must have been in the mud. Of course the Boutonne is running water and my little pond isn't. I just feel I ought to put it back in the river.It's is about 4" long. I think it might eat everything else up. It seems to like swimming near the bottom of the pool. Advise please. Thanks