I posted this same question on another forum, but I also wanted to get some insight from you all here:
I have a single Guianacara sphenozona, that is 2-3 years old and about 6"long. I do not know if it is male or female, but I suspect it is male due to it's aggression toward tankmates. He will often be chasing the two Green Severums (each about 4-5") or poking at the two Clown Loaches (each 4-5"). I also witnessed him chasing and nipping at former tankmates, now deceased (2 Gold Gouramis, 2Thorichthys sp. "Blue Mixteco" , 1 'Geophagus' steindachneri). I never saw him chasing the smaller Red Eye Tetra in the tank, or bother with the pleco.
So my question(s) is this, is he just a bully, or is this something else? Does he need more Guianacara sphenozona in there with him? Does he need to be in a tank alone? Should I look to re-home him? Any insight to this would be greatly apprecieated.