detritus eater

I'd simply use gravel vacuum cleaner. Don't rely on fish to work for you. Besides most fish will love to wipe out invertebrates.;)
 
any fish you add will be contributing to the detritus. use the gravel vac
 
Adding in a snail or two would be the only suggestion I have. They will help keep the plants, glass, and substrate clean of algae/bacteria. They also won't bother your other invertebrates.

You will still have to gravel vacuum and keep up on water changes.
 
yabbies will wipe out any fish/shrimp you put with them.
 
if you mean detritus as in leftover food, feed less. if you mean it as in poop, no. no fish will eat feces as a mainstay of their diet. even those that appear to eat feces (like cory cats) really are just shuffling through it in their search for real foods.

in addition, any time you're asking a "what can i add?" question, it's best to put the tank size somewhere in your post. it makes for the most appropriate recommendations.
 
deitriius is what seems to build up and is an indicator that the food is not being eaten or it's being eaten and released too often... another indication that overfeeding is going on. There are fish that take care of any food that might fall to the bottom of the tank, any bottom feeder can do that but if it is feces, there isn't a fish in the world that delights in ridding the tank of it. This deitrus you are having a problem with, it's always a fail safe method to perform weekly water maintenance such as water changes and vacuuming will help clean that up. Adding fish will only add to the problem.
 
AquariaCentral.com