I'm trying to figure out if I'm overstocking this 125 gallon (72 1/2 x 18 1/2 x 23 3/8)
Filtration: Marineland C360 or Fluval 406 and 2x Marineland Emperor 400
Fish List:
1x Oscar
2x Firemouth
2x Blood Parrot
1x Fire Eel
4x Angelfish
3x Rapheal Catfish
6x Silver Dollars
Thanks

wwww.aqadvisor.com is a good starting point to check.

1x Oscar (center fish)
2x Firemouth (nice addition)
2x Blood Parrot (ugly man-made hybrids, wouldn't add them, can be very agressive)
1x Fire Eel (unless you buy it big enough, it'll be a snack for oscar)
4x Angelfish (will be bullied by oscar very easily, can't defend or escape well)
3x Rapheal Catfish (nice bottom feeder, mostly hides during the day)
6x Silver Dollars (nice addition too, but can be very skittish when not being fed)

my suggestion for your tank:

1 oscar
2 firemouth
3 raphael
6 silver dollars

be aware that sd's are lawn mowers and will eat anything offered, so make sure to feed the raphael when the lights are out)