I recently moved and I did have mbuna cichlids in my 55. I want to try south American cichlids when I put my tank back together. Can anyone recommend species that are not too too aggressive? How about Angels? What kind of substrate should I put in the bottom of my tank? I'm not sure if I want to go the gravel route again or if I should do something different. The tank is going to be in my living room so I want it to be interesting and nice looking. Thanks for the help!