I started my 200 gallon tank with One Piraya, when I got him he was about 4 inches. after about three months I wanted to spice things up so I put in three reds with him. In a years time he proved to be the boss of the tank. he started to pick on all of them except one. I had to remove the other two because he would of killed them. Now two years later my Piraya (Fred) is close to 12" long and 2 and a half inches thick. He gets along fine with the other red who is about 7 inches. every now and then he chases the red around. That means it's feeding time. I feed mostly fresh salmon. But I freeze it first for 48 hours to kill any parasites. I then thaw it and rinse it well to remove as much oil as possible then cut it in strips and feed. They love it! every now and then I will treat them with Live feeders. I change water, 30% every week. I have a good filter system and great water quailty and yes I do add salt to my tank. I keep the temp. at 82. My goal is to get (Fred) as big as possible. At the rate he is growing and eating I think I should be able to reach the 16" range in a year or so. I will post pictures soon.
Rando