Some shrimp sift through fish poo to collect anything that didn't get digested. They also can reach into the tiniest cracks to get food that was missed. In my tank, I feel a herd of Ghost Shrimp goes a long way to keeping things clean. Sifting through the poo breaks it down, IMO, into something the bacteria colony and plants can readily use.
I understand Amano shrimp are algae eating wonders, too.
I like how I can see what the ghost shrimp are eating, since they are clear. If their stomach is red they ate fish food, if it's green they're finding algae ... Good to know.
They're also interesting to watch. And ghost shrimp cost a few pennies. They don't live long ... However my well cycled 29 gallon never has a water chemistry problem when one dies, dunno if this is because they're so small and the other shrimp eat them or what. In fact I've almost never seen them dead, just one and I'm pretty sure I've lost about 5. Obviously dead critters should be removed if you spot them but mine just vanish.
