Ghost shrimp will surely help to keep your substrate clean of detritus, the ones I have and have had are constantly picking at leftover food and poo and algae. They will also grab some live food if the chance presents itself. I found one of my ghosts working on some algae on a leaf yesterday, hooray. Buy you'll want a small army of shrimp to really keep up with the job. I would suggest 1 for every 2 gallons if they are the only things cleaning. You can always get some Cherry shrimp on Aquabid too. I've gotten two batches so far on Aquabid and have quite the little community going in a couple of tanks. Ghost shrimp are cool though (and cheap), just beware they are considered feeders and are potentially more prone to parasites. I've seen a number of them in my area with a thread-like worm in their body, which upon researching, found out it will eventually bust out and look for other hosts.
Our Walmarts in NE Ohio stopped carrying fish, but when they did carry them, they always stocked one or more varieties of Corydora. These guys really help keep things clean as they root around the gravel constantly. Might want to consider a group of Cory cats.
Also, some folks hate snails and claim the generic ones hurt plants, but I haven't seen much evidence in my tanks that they are detrimental, and I have lots of them in a couple of the tanks. They are good for processing leftovers into nutrients that are more readily available to your plants.