I had a "trio" of Lyonsi in a 1000g tank for a while and they were completely peaceful. Sometimes a little chasing between each other, but nothing more. I think they were about 8-10" when I re-homed them. Some of their tank mates included cichla, A. sagittae, a breeding pair of P. bifasciatus, salvini, oscars, H. psitticus and a large Fossorochromis rostratus that I adopted. Very personable fish and very pretty.