Quote Originally Posted by JCO

If your Tilapia are of that age, it will do the guppies not good to group and they won't last long enough to reproduce to replenish their selves either. They'll be history in a short - short.
Probably so, but I had a half dozen gambusia (mosquito fish) that peacefully coexisted in a fish tank full of tilapia up to 3 pounds for nearly two years. They showed no fear of the tilapia and the tilapia never showed any interest in them. The gambusia started out about an inch in length and were approaching 3 inches when I relented, netted them out and set them free in the canal where I originally acquired them.

I thought it strange that the tilapia would devour tree frog pollywogs with relish, but totally ignore the gambusia.

Another interesting anecdote about predator fish: Some Years ago, I kept Oscars. One, a large red Oscar I called Napoleon, had a tank to himself. Every couple of weeks, I would spring for a treat for Napoleon and bring him a dozen feeder goldfish from the local pet store. The first time, he almost instantly devoured all the fish, but one little goldfish he allowed to live. In subsequent live goldfish feedings, he would immediately devour all the fish, but always left that same goldfish unmolested. The goldfish showed no fear of Napoleon and would frequently swim right past his face. They lived peacefully together for nearly two years. I found that both amusing and amazing!