I have 15 nerite snails, 6 amano shrimp, and 2 bristlenose plecos in my 55. Love the amano shrimp! They are extremely active cleaners and will clean everything but the glass in your tank, but not recommended with the fish you have.
Nerite snails are great except you will probably need a lid on your tank, and eventually have eggs all over your plants and driftwood. I'm not sure how much of a benefit the bristlenose are as far as eating algae, but my wife have become very fond of them, and I love how they wont get much bigger than 3-4in.