Cyps don't count as "carnivores", and you might not dare it, but in a roomy tank and in the hands of an experienced keeper; Cyps and Tropheus can mix quite well.
you need to get the more robust Cyps; Jumbo-types or true leptosoma. I wouldn't try it with pavo and certainly not with microlepidotus.
actually I did try it with microlepidotus and let's say I wasn't exactly covering myself with glory there.....
don't do it.
but "regular' Cyps are fine.
the trick here is cyclops
cyclops is perfectly safe with tropheus! it has a hard shell (fibers!), it's minute (so tropheus usually miss out a lot) and it is THE favourite food for cyps.
on a diet consisting just of prime quality veggie flake (OSI, NLS, Wardley, Hikari etc) and cyclops you can succesfully breed Cyps.....
As for Cyps with Featherfins: it's a match made in heaven, but to avoid too much agression I'd leave the Jumbo types for what they are unless your tank is nice n roomy. and growing them up together (starting with juvenile jumbo cyps and juvenbile Featherfins) usually works.
I've experienced with Featherfins that yes, they are vegetarians, but far less strickt than Tropheus. you can give a Featherfin food that you wouldn't feed a tropheus. so the Cyps will thrive even better.
Cyps and Featherfins in a 240G? NO problem!
Paracyps might get a bit stressed by the hyperactive Featherfins. but if you like the combination of the reddish-brown-blue of the Paracyps in with the green-brown-yellow of the nasuta's, you might think about Cyprichromis microlepidotus.
they DO handle Featherfins just fine. I've kept 24 C microlepidotus 'Mabilibili' with 10 Cyathopharynx foai 'Kabogo' in a 132G and the colors of both species were amazing.......
Go and get a nice contrasting Cyp for your nasuta's; you will not be disappointed!
ps: as for cavedwellers: there's a load of cavedwellers that do just fine on a fairly veggie diet. they are often overlooked cause they are either viewed as "Beginner Tangs" (Julidochromis) or "lacking in colors" (Chalinochromis, Telmatochromis).
In that 132G was a breeding pair of J regani 'Malagarasi' and a breeding pair of Telmatochromis dhonti....the latter has a very bad rep as the ol' "caninus" (doggie fish?), totally undeserved cause the featherfins only harmed themselves.
you wouldn't believe the numbers of fry I got from those omn that veggie-cyclops diet!
"And he piled upon the whale's white hump the sum of all the rage and hate felt by his whole race. If his chest had been a cannon, he would have shot his heart upon it"