Missed the update on this... wow! That's looks soo cool! Makes me want to extend the back of my tank upwards... that would be a cool product, a wall that
On thin filter pads... the aquaone above tank trickles take about 15x6x1cm thick course foam pads - expensive for the branded ones but knockoffs available on ebay.
The badis are great, my favourite fish at the moment. So dinky, but mine will happy eat a full size daphnia - might just be yours have a little growing? The completely ignore adult cherrys... I imagine they pick off the babies well as they are always prowling about hunting. No issues with them in with ember tetra, otos, habrosus cory. They watch their prey before pouncing so would definitely be at risk of our competing with anything to quick. At least with live daphnia you don't need to worry so much about over feeding so everyone gets some. I think they are the perfect choice for this tank though, they look really good!