What are the pros and cons of using irish moss versus whirlfloc tablets for clarifying beer?

2 Answers 2


I used Irish moss for many years before switching to whirlfloc. But I think that was an availability thing more than anything else.

Irish Moss:
PRO- Works great everytime.
PRO- Cheap
PRO- easily scaleable to any size batch
CON- Need to measure it out

PRO- Works great everytime. I found it was even mildly better that IM, but that's tough to call.
PRO- Tablet is great and no measuring required, 5 gallon/s per tab.
CON- Tablet doesn't easily allow for a non-5gallon interval brew (say you did 8 gallon batches or a 3 gallon batch) This is trivial, but you could in theory over do it if you were doing small batches.
CON- More expensive than IM, but we're talking nickels not dollars.

In my experience whirlfloc is easier to use, with few draw backs. But in real world application the two are practically the same performance wise.

  • 2
    I'd been told that Whirlfloc was 10 gallons per tab. Commented Mar 5, 2010 at 12:54
  • Interesting. The whirlfoc I buy says 5 gallons per on the bag.
    – brewchez
    Commented Mar 5, 2010 at 13:01
  • ... aaaaand I guess I was misinformed! Commented Mar 5, 2010 at 14:32
  • Boy, that extra nine cents a batch is really going to hit me in the pocketbook. Srsly, I'm glad I don't need to split the things up anymore. Commented Mar 5, 2010 at 14:33
  • Google "whirlfloc half" and you'll find plenty of sources suggesting using half a tablet for 5 gallons.
    – Jeff Roe
    Commented Jul 6, 2014 at 16:27

In my experience, Whirlfloc works better. I used Irish moss for my first couple of years, until I found Whirlfloc. The first time I tried it I was amazed at how clear my wort got. I chill by putting my kettle in a tub of cold water, and the visual effects of a Whirlfloc-treated wort when it hits about 25 degrees C are pretty cool. I've never seen anything like it in my Irish Moss batches.

Yesterday I did my first batch going back to Irish Moss (I ran out of Whirlfloc) and it did not clear nearly as well as all my Whirlfloc batches.

Maybe I'm not using enough Irish Moss. I'm using about 1 tsp in 5 gallons, re-hydrating it in warm water before putting it in for the last 10 minutes of the boil. I think I'll try a couple more batches with IM, but if I don't get better results I'm going back to Whirfloc.


I should clarify that I'm talking about pre-fermentation clarity. I get crystal-clear wort when using Whirlfloc, but I don't think I've ever seen that with Irish Moss. But I'm not sure about the difference between the two post-fermentation. I always have significant chill haze with both, and I haven't really compared the two. But I've found that pre-fermentation the difference is striking.

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