I recently purchased a 55 gallon tank. ATM its maturing so I can put our fish in their new home. However, they are only 3 fish and its a 55 gallons tank. I am planning on heading to St. Louis to get some new colorful fish.

requirements:
semi-hardy to hardy
freshwater (only)
cannot get bigger than 6-8 inches in length
peaceful
colorful

Any suggestions?

I am thinking of a few already but need more.
Tropheus Moorii
Ram (a pair)

Oh yeah, how easy is it to grow freshwater plants?