One shrimp is fine. Chop it until its minced. You could use a mesh bag but i added mine directly to the tank. The bacteria will feed on it and at the same time, it will rot creating ammonia. It won't sit at the bottom for long if you are worried about a mess. You should join aquaticconnection.com . I'm mostly posting there now. You will also get more help there than just me. Seems as nobody else knows how to reply here. I stick around here and try to drag over those who are serious. You could start a thread asking for help or even start a journaled thread all about your tank with pics. Anyways, did you get a test kit? The most important tests right now are ammonia, nitrates, and pH.