tank for rhom

I'm thinkin about getting a rhom, a small one that will be with me for a very long time. What size tank would work well for a solitary rhom? I want to do red sand with a black background, but does anyone know where i could find red sand? I was going to get a large tank and get a shoal of rbp's but i think it would be more conveinant for me right now (since i will be renting a house) to have a smaller tank with one fish. Anyway yeah, size, shape, any general knowledge would be helpful.