I've had a container garden for about 3 weeks, pots filled with Miracle Grow container soil and a little bone/blood meal.

After Fay came through I went to check on my pots. One was flooded with DOZENS of 1cm white worms under the water. Some were still wriggling but most of them appeared to be drowned. I saw one of these in some soil I removed to germinate some seeds inside, but what I saw this morning was literally dozens.

Is this something that came in my potting soil, or something that was lain there after the fact? Are these pests or beneficial? They're not maggots, but I don't know what they are. If nobody knows I'll post a pic tomorrow if I can.

Thanks!