I have a book of cichlids. One of the jumbo cichlids looks similar to (in nose) as the Labeotropheus Trewavasae from Lake Malawi. The nose is down like on a shark. This fish according to the book grows to 10cm but the fish I saw was huge. He was on steroids or something.
So what tank size would be suitable for a larger cichlid of 6-8 inches? It's a bit confusing with africans. You have to crowd them but if they are around 8 inches a 55 gal is too small?
Here's the cool part with africans... There are tons and tons of possibilities. Larger fish like haps which grow bigger than 6", imo, need a 6' tank minimum. Smaller africans like mbuna (most of them at least), peacocks, alot of the tanganyika fish do just fine in a 4' tank.
There are some mbuna that do best in bigger tanks. Acei are very active fish, and get around 6-7". They'll do fine in a 55g, but do enjoy the extra room in a 6' 125 or bigger.
My suggestion is to do what I did. Use google to find fish that you like. There are tons and tons and tons of threads on this forum and other forums that have suggestions, pictures, or at least names. If you cant figure out what a certain fish looks like, go
here and you can find practically any cichlid ever discovered. They almost always have a picture and some info in regards to their social activity, diet, and tank requirements.
As far as the fish you're describing, the Labeotropheus sp, IMO, look alot like the Melanochromis sp in terms of body shape. They have the torpedo look when compared to other fish like the Labidochromis and Metriaclima sp. I've never seen any of the Labeotropheus or Melanchromis species get over 5-6". I dont know much about the victorian and tanganyikan species though, but I'm pretty sure none of them get all that big. I almost bet a fish that big (unless you just totally misjudged its size.. easy enough to do) is a Haplochromine, but I dont know of any off hand that have a similar body to the manda or mpanga