i have a 55 gallon (in my opinion the worst size tank) its a hardscape with driftwood, rocks, and nautral lighing currently stocked wiyh 6 emerald corydoras , im looking for a large south american fish (around 5-6 inches) i really like the look of silver dollars and that body shape but have read that a 55 is most likely to small. This my first post so please forgive me of any mistakes.