Stocking A Rio 300

[Carolinesugar]

Hi All, I have recently moved into my own flat, and have upgraded my fish tank to a rio 300.

At the moment, I have the following fish in a planted tank, which has alot of rocks, wood and hidy holes:

Common Pleco
baby snowball/vampire pleco
4 peppered cories,
16 pygmy cories
4 black kulie loaches
2 olive knief fish
1 butterfly catfish
6 marble hatchet fish (just added these today)
2 candy stripe gobies
3 orange platies
3 orange swordtails
1 ruby shark
1 flying fox

I was wondering what you thought I could add to the tank as a surface or top of the tank swimmer.

Any ideas are welcomed!