I saw that, the Lemon (or yellow) damsel I think it was. I also saw Green Chromis mentioned. I wasn't planning on going the damsel route, are they more aggressive than the six-lines?
I have been flatworm free for the last week and a half! Thanks to those who recommended flatworm exit. I was becoming weary since so many were left after the two initial doses but I guess some of them were in the process of dying still.
I also picked up a yellow wrasse this past weekend, so if any are still around hopefully he will keep them in check. He appears to be "hunting" when he is awake and out of the sand. Very active and very colorful. For the past two nights I was able to watch him jump into the sand bed for his sleep. So cool.