Good suggestions, although I wouldn't go with the istlantum, a little to close in torpedo shape and coloration. the rest of the tall bodied species with competely differant color schemes would work probably pretty good.
dither fish is my answer to stop aggression my 210g: 14" Bocourti, 7"carpintis, 7"f.grammodes, 5''m.grammodes, 5"m.istlanum, 4-5".jaguar catfish, 2-3".clown loach, 8-lrg silver dollars. very peaceful tank I can spend hours watching them.
calicichlid that is rare that you would have a peaceful tank with all the cichlids mentioned in a 210 gallon tank. I have a 360 gallon tank and have problems with grammodes sharing tank space, let a lone Istlanum...
I agree with cichlid fever, especially if they are a bonded pair, I doubt if any tank mates will be allowed to live, and they need a tank of their own.
I grew out a 1" group of 6 with some live 3-4" bearers.
The emerging pair killed all other grammodes by the time they were 3", and the live bearers, and wouldn't allow any other fish (much less any cichlids) in their tank.