Peppermint shrimp: I have 2 in each of my tanks and they've decimated the few Aipstasias I had. Dunno if there's a formula for how many, but 2 does well up to a 57 gallon tank. They are the assassins of the shrimp world, they reach into those aiptasias and rip their stomachs out, kinda gruesome but cool. I sat in amazement the other night watching one do his thing wishing the battery in the camera was charged! Scarlet cleaners: Used to be my favorites till they went on a spree killing my green bubble coral. I don't know if the coral was on its way out or not, but they were all over it like ugly on an ape. Needless to say they are residing in someone else's tank now. Saron shrimp: Cool critters, very secretive with a taste for tridacna clams. Came home on leave to have the wife tell me she watched it rip the innards out of our clam in the 240. When it sloughed the Comet ate it, good fish. Sexy shrimp: Love them, innocuous as all get out, very hardy despite their frail appearance. Blood shrimp: Another one that is very secretive, I love them, but I want critters that I can see once in a while, more than once a month, lol. Camel shrimp: Not a good mix with Comets, they think they're a tasty snack, lol. Found that one out after the 4th ones antennae was seen as it was going down the Comet's throat. Anyone else have other species that they wanna talk about, go ahead. There are so many different species available now compared to when I had my last tank and the shop in the late 90's.