I am a total nOOb but I can tell you what I am doing and maybe it will
point you in a direction...

I have a 55 gal with Malawi Cichlids, in that tank was a male rusty who was
being beat up all the time

he is an Iodotropheus sprengerae

I put him in my 20 gallon (happens he matches my bedroom walls btw which is
a bonus), and I put in some lava rock (Lace rock in the 55gal) and I just
put in two female rustys... I will put in 4 more female rustys in my 20
gallon.

This is a link that you may enjoy (the rustys stay small but they aren't as
colorful as the others, I like the personality I see so far)

http://www.thetropicaltank.co.uk/Fishindx/sprenger.htm

Hope that helps a little.