I agree, I had 2 in a 55 gallon a few years back, they seemed to get along great until they got bit larger....maybe about 4" or 5". Then ll he** broke loose. Each "owned" 1 half of the tank. If one came remotely near the mid-line, the other came out charging. Eventually, I noticed one had a big chunk bitten out the side. The next day, the other had one too..... before long, both of them had fought until they were both too weak to carry on....... I advise against it...... I learned that if I wanted to venture the RTS avenue again, it could only be one to a tank at the most.....