Um..and you are wanting to add these fish with your current mix? even in 200 plus gallons the truely peaceful fish that are mid sized will have a stress-out with the acaras at breeding time alone.
Why peaceful specifically? the eels? Are they meant to be snacks? Are these ray types fish eater?Or small stuff snackers?
Most colorful peaceful things are small for this lot of fellahs.
Maybe silver dollars ? Pacu? But balas are just the same colors there. And they can be stinkers too. What are you wanting these fish to do?
I guess I just don't know.
Color and not be expensive snacks and not be aggressive..maybe a whole monster shoal of platies in riot of their available colors? or something like the larger tetras? A big mixed shoal of tetras and take the occasional 1-3 missing? maybe a bunch like emperor in red and blue, penguins and HATs
How about some semi-aggressives? Rainbowfish, Gourami
Angels? They are an expensive snack..... I've never kept anything large enough and not be peaceful. Unless you are well planted for gourami to nap at the top levels, they really like sleeping at the bottom often. Your bottom is busy. As far as size and temperment, kissing gourami would fit. But they are not all that colorful.
I don't think any of the fish I know well are suitable really. If you say WHAT function the fish are to fill, maybe more answers will crop up...