irish moss is used to clarify beer when boiling the wort. Heavy proteins adhere to the irish moss and settle out, I use it each time I brew and my beers have been very clear. A quick chilling of the hot wort also cuts down on what is know as (chill haze) and makes the beer nice and clear. I haven't used a yeast nutrient yet and have found that buying a good liquid yeast (slurry) in a tube (cost - around $5.99) is well worth the expense, and very, very easy to use. Any good home brew supplier can recommend the liquid yeast ( Wyeast is a very good brand)

In Reply To #1 I used to use Irish Moss, but found that Whirfloc-B tablets work a little better. Whirfloc is a tablet form of Irish moss and gelatin. They clear up the beer very nicely. The only time you really need to add yeast nutrient is when you are making a high gravity beer. As the beer is fermented, and the alcohol levels get high, the yeast tend to quit. Yeast nutrient keeps the yeast healthy and strong enough to tackle brews with a OG of 1.080 or higher. Nutrient is not neccessary on lower OG brews. Again, make a starter to make sure you have a healthy yeast culture. Pitching just a packet or vial will work, but you won't have a very healthy yeast. Also, a starter drastically lowers your lag time (the time between when the yeast was pitched and when it started fermenting). This is a vulnerable time for your beer and when it is most infection prone. Starters, always.