Question split into it's own thread. I'm fairly certain that once full grown either the goldfish or the angels would mostly stock the aquarium by themselves. I'm sure someone who is more familiar with those fish will be able to tell you for sure.
Those fish are not compatible. The angels would work, the goldies would work, but not together. The knife will get to large for the tank. If those silver sharks are what I think they are they will get big and need brackish to full salt water as they grow.
You need to decide what you want and return some fish before they get large and you will have problems moving them.