If I was you, I'd drop the African knife fish, most species get to be 10", the reedfish are going to get too long for that tank, so I'd drop them aswell... For the Catfish, I suggest either A pictus catfish, or African Clown catfish. Also, as already said, the silver dollars will get too large, I'd say don't even get a school of anything because you also mention you want two other oddballs. What species for the other 2 oddballs are you thinking?