A long time ago, one of my “must have” species was Altolamprologus calvus. A physically unique cichlid from Lake Tanganyika, calvus are laterally compressed so they can get into rock crevices to both feed and breed. They also possess special flank scales that serve as a type of body armor. These fish will turn broadside where they are most protected to absorb attacks by predators and even conspecifics. These flank scale edges are quite sharp and can inflict damage on their own.
I started my calvus journey with three juveniles about 1.5″ in length – what turned out to be a female and two males. I housed them in a 75g Tanganyikan community tank with other Tangs. All went well for the first four years with very little aggression toward each other or any other tankmates. In year five, however, the two males became extremely combative with each other. The one real fear I had with these fish was their propensity for jaw dislocation. I had read many times that they can end up with dislocated jaws from sparring and other issues.
Beginning in year five, the two males began to lock jaws quite frequently. This went on for months with no real damage to either one except some abrasions around the lips. That all changed overnight a few months ago.
I came downstairs to my den where my show tanks are. I noticed the lower jaw of one of the males looked funny. It almost appeared like something was in its mouth (maybe a small fish). I didn’t immediately think much about it. Noticing it still there the next day, I netted the fish and examined it.
The lower jaw was so mangled that bones and cartilage were visible inside the mouth. Basically, the lower jaw had been broken in half right down the middle. The fish continued attempting to eat and was able to inhale pellets. I naively thought it might be able to survive because of the pharyngeal jaws as long as it could get food to them. The injury didn’t seem to affect the behavior of the fish at all. I ended up putting it into a segregation tank but, sadly, I couldn’t save it.
While calvus are beautiful fish, I would not recommend more than one male in anything 75g or smaller because of my experience.