Ok, so I've read any number of times here that aquarium livestock sold for a specific purpose rarely do a good job at what they are sold for. I understand that. My question is, besides looking interesting, is it actually beneficial to the eco-system of a freshwater tank to add invertebrates such as shrimp? I'm asking because i'm seriously considering adding a couple red cherry shrimp to my 20g tank as tank-mates for my guppies. I read that they eat a lot of the detrius that build up in the substrate from fish waste, and feed a bit on algae as well. Is it enough to make a noticeable difference in the tank?