What kind of invertebrate?

[kitnerjr]

I want to add an invertebrate into my tank to help clean up the bottom of the tank, as well as add some variety.

55 gallon - Freshwater
AqualClear 70 Power Filter
Fluval 205 canister

peacock eel
pink gourami
2 dwarf gourami
2 balla sharks
african butterfly

Any suggestions? I was looking into something like a hermit or crab.