definatly on the bottom feeders thing go with a bichir of some kind. they're predatory and i knwo u said u like active fish and bichir are super friendly, my ornate bichir acually swims up to my hand and brushes against it.
I was thinking that but there is two problems a)i would have to find a pair and not two males and b) i like my tanks to stay the way i made them so couldnt cope with cichlids digging up gravel and my plants
but another thought on a fish is maybe a Mbu or a fahaka(fahaka more likely because of smaller max. size) puffer because i know they're both REALLY aggresive and im pretty sure all puffers are super active, theyre beautiful also
I was thinking of your preditor wants, I thought you might like ropefish, the only thing is make sure that you have a tight fitting lid. They are very beautiful and you can keep a bunch together. Just remember if you find one out on the floor to put it back in the tank, they can survive up to 8 hours out of water.