I will tell you from experience that Tropheus can be difficult to keep with Calvus as they have different diets. Tropheus have evolved to graze algae all day right down to the mouth and jaw structure and their digestive system is built for digesting algae, not worms and protein packed food. Their intestines are longer than most fish to absorb the most it can from the algae they eat and eating high protein foods, especially foods with high fiber as well is very hard on the digestive system causing bloat. Typically the dominant male will eat up all the food and if he eats to much of the whatever you're feeding the Calvus, he could very easily get bloat. I've seen it happen a few times and it's always the dominant male that gets sick sometimes the subdominant as he/they are the ones inhaling the food at feeding time. If it does you have to remove it ASAP as it has already done irreversible damage to the internal organs. Tropheus are by far my favorite African Cichlid. Saw a great presentation on Tropheus at the last ACA convention here in Denver. And we have a few Tropheus tanks in the house, all my brothers but I really enjoy watching those fish.