*Ctenopoma acutirostre (required planted tank), this species will prey on small fish and hard to get them off live feeders.
**Exodon Paradoxus also required heavy planted tank and a large school (25+ Exodon). You can't add anything that small and have scales on their body to this tank but cory cats, octocinlus (algae eater if you do planted tank), yoyo loach work fine for bottom dwellers.
***Rock or driftwood only tank and get 1 or 2x blue, white crayfish (common name blue/white lobster in LFS), I would refer 1 blue and 1 white, you can semi planted with hardy plant like Anubias but beware crayfish will munching on plant if not well fed. Those crayfish will control the bottom so the mid/top dweller you can try to get a shoal black ruby barb (get a shoal with lot of male ruby and few female then you will have a awesome color display in your tank).
****Solo a Juv. Serrasalmus Elongatus, this species growth rate notoriously slow so it will last in 45g for long time.