I need some help to figure out what I need for a cleaning crew. I have 120gal tank with nothing but live rock in it atm (about 100lbs worth) Can anyone tell me the numbers of snails, crabs, stars, shrimp i might need for this size aquarium? I have looked at some of the "packages" you can find at online stores but I am not sure I like the mixes they offer. If anyone can help it would be appreciated.