Fermonster Carboy - 3 gal.

Fermonster Carboy - 3 gal.

Accessories for your Fermonster  
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The Fermonster is a brand new fermenter designed specifically for fermentation. MoreBeer! gave product feedback for over 2 years of development and we think they nailed the design. The large lid allows for easy filling and makes hop or oak additions a breeze. The smooth sides are fantastic for sanitization - no ribs or texture to collect yeast or bacteria. The punted bottom allows sediment to collect to the sides so that you can siphon liquid from the center.  Because they are made from virgin PET plastic they nearly unbreakable and a lot safer than similar glass carboys. Also notice the conical top which reduces surface area if you plan to store beer or wine long term.  

Made from heavy PET plastic, the same material used in 2 L soda bottles, which is nearly impermeable to oxygen penetration.  Due to the thickness of the material and the overall geometry the Fermonster does not require ribs or dimples for stability.  That results in a super smooth interior surface that reduces yeast and sediment buildup making it the easiest to clean, most sanitary PET carboy on the market.  The huge 4" opening makes filling a breeze, and cleanup is as easy as wiping down the inside.

These fermentors are completely air-tight and the lids sealed tight with an O-Ring.  Additional O-Rings and Lids both with and without holes are available for purchase, see our You Might Also Need items below.


  • 4" inner diameter wide mouth carboy - easy to clean!
  • Food grade PET plastic construction is nearly impermeable to oxygen penetration
  • No hard to clean dimples or ribs
  • Punted bottom
  • O-Ring and Lid with one hole is included (Fits #10 Stopper)
  • Additional O-Rings and Lids available
  • Weight: 1.5 lbs
  • Temperature Limit: 140° F
  • Height: 14.6 inches
  • Diameter: 9 inches
  • Completely taste and odor free
  • Perfect for Beer, Wine, Cider, Mead, Kombucha or any other fermented beverage!
  • Thick walls for better oxygen barrier.

Please note: the pictured #10 Stopper (FE470VS) and three piece airlock (FE370) are not included.

Item # FE258
Shipping Eligible for Free Shipping Program
Availability California - In Stock
Pennsylvania - In Stock
Weight 2 LBS
Community Q&A

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Browse 4 questions Browse 4 questions and 7 answers
Why did you choose this?
MoreFlavor Store
Split 5gal. batches
Jan Lawson on Dec 21, 2022
Need an extra
Lori W on Dec 16, 2022
Split 5gal. batches
Jan Lawson on Dec 21, 2022
need to make bigger batches
Michelle S on Dec 20, 2022
Need an extra
Lori W on Dec 16, 2022
Wanted a larger fermentation vessel
Lori W on Dec 14, 2022
Valued C on Dec 8, 2022
Valued C on Nov 23, 2022
for making rice wine
gilbert b e on Nov 3, 2022
The size and addition to one I have.
Tony S on Oct 21, 2022
Nancy Carlson S on Oct 14, 2022
Been using these for a while and wasn’t an extra
justine Van S on Oct 12, 2022
good for smaller batches
James L S on Oct 7, 2022
Have a couple smaller batches of wine i want to make
Brian B on Sep 14, 2022
Racking Container
Akiva Y S on Sep 9, 2022
Need a car boy for my new 2.5 gal keg
Christine Sotelo on Aug 30, 2022
Wanted to split a 5 gal batch
Joanna M on Jun 21, 2022
want to make small batch stuff and ciders
Gerard S on Jun 18, 2022
making 2.5-3 gallon batches of beer, need fermenters
Brian B on Apr 11, 2022
TO increase my current brewing capacity
Gerald D Z on Mar 28, 2022
I already have 2 and I can see what's going on inside I really like that
Daniel R on Feb 10, 2022
Trying out something new!
Troy S on Jan 29, 2022
to age mead in prior to bottling (4-6 months)
D.Murphy on Jan 22, 2022
Upgrading my mead setup
Alan Bell G on Dec 19, 2021
BRIAN J S on Nov 8, 2021
Someone suggested it to me for making homemade wine.
Brenda G on Oct 8, 2021
Making peach wine
Theo Macris on Aug 27, 2021
I switched to smaller batch sizes, and also wanted something with a wider mouth than my better bottles.
Christopher D on Aug 17, 2021
Need another
Randy R on Aug 17, 2021
I need another fermenter for a secondary
Alfredo Trinidad on Jul 29, 2021
to make dessert wine kits which are 3 gal size
Alison G on Jun 22, 2021
Made of PET, good lid, correct size
Dave A on Mar 24, 2021
looks cool and its not glass
Irma U on Mar 9, 2021
Less volume
Eric Pineres on Feb 11, 2021
I frequently brew smaller batches and this should be helpful.
Matt Burns on Feb 9, 2021
i have a small brewing fermenting spot in my place and i dont make large batches. as often i have a 6.5 and a 5 gallon carboy time for a 3 gallon wide mouth
Shawn B on Jan 29, 2021
Need more volume flexiblity with wine making
Jared B on Jan 27, 2021
Will try for making Sake
Jeff L on Jan 25, 2021
Trauma Nurse on Jan 8, 2021
Easy to clean
Jill W on Dec 31, 2020
I am making more meads and would like to something other than 1 or 5 gallon batches.
Jon Davison on Dec 18, 2020
I like this size for mead
Traci K on Dec 1, 2020
I like this size for making wines and meads
Tracy K on Oct 28, 2020
need it
Paula LaRocca on Sep 26, 2020
need a bigger fermentor
Alfredo Trinidad on Sep 24, 2020
good size for small batches, easy to clean
John L on Sep 17, 2020
Not glass.
Charles A H on Aug 28, 2020
Nice half-size container for experimenting with 5gal batches, such as adding different quantities for dryhops/additions, etc
Cameron L on Aug 7, 2020
Fits well in the fridge!
Nelson E. Vera S on Aug 4, 2020
get away from glass
keith k. on Jul 15, 2020
Smaller baches
Xavier E on Jul 2, 2020
Small batch testing
sean r on Jun 13, 2020
need to make bigger batches
Michelle S on Dec 20, 2022
Wanted a larger fermentation vessel
Lori W on Dec 14, 2022
On the larger versions, the line near the top where the sides begin to slope indicates there is one gallon of space left. Is that true for the 3-gallon version as well?
Douglas Frazer on Aug 17, 2018
BEST ANSWER: It's 3 gallons at the crease. I haven't done a fill test to see how much more liquid it could take to the brim, but it's definitely not another gallon -- maybe 1/3-1/2 max. I'd put money on 1/3.
Any plans to offer this size with a spigot?
Tom Meskill on Jun 8, 2018
BEST ANSWER: We are always looking for new solutions and products. No confirmation if this will be manufactured with a spigot, but it's not out of the question. You could attempt drilling the plastic yourself.
Can the 3 gallon Fermonster be used to ferment a 2.5 gallon batch?
Warren Parker on Sep 13, 2018
BEST ANSWER: Hi Warren - Should be okay, ferm caps couldn't hurt either.
Foam Control (FermCap S) (1 oz)
Foam Control (FermCap S) (1 oz)
Are the side walls thick? I purchased a 1 gallon version and am disappointed on how thin the side walls are compared to my 6 gallon Fermonsters.
Justin W Thomas on Jul 20, 2018
BEST ANSWER: Hello Justin - The side walls of FE258 and not quite as thick this as those on FE250.

4.0 / 5.0
24 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star
Rated 2 out of 5
Bad O-ring fitment
The carboy arrived promptly and for the most part as described. The only issue is the o-ring (and the spare I bought) are of a miniscule diameter of rubber and a tad larger than the groove they set in.
Getting the o-ring to remain in place while attaching the lid is difficult, already had to retrieve it once from my incomplete must.
January 10, 2022
over 2 years ago
Rated 5 out of 5
Always great stuff. Very quick turnaround as well.
December 24, 2021
over 2 years ago
Rated 5 out of 5
Have Five Now and All Are As Advertised...Mostly
Sometimes when your grape harvest is off a bit, you need something smaller than the typical 5, 6, or 7 gallon size carboy. The Fermonster 3 gallon sized is just about perfect when that happens. Just as for the others in the Fermonster line it is easy to clean, easy to sanitize, easy to fill and if you install the o-ring correctly, is air tight over the long term.
August 20, 2021
over 2 years ago
Rated 5 out of 5
Overall this is a good, inexpensive little fermenter.
Used this 3 gallon carboy to ferment a 2.5 gallon test batch. The plastic made it very lightweight and easy to handle. I’ve heard some concerns about the o-ring in the lid but there are several YouTube videos that explain how to put in in so it wasn’t a problem. Cleanup was really easy since you can put your whole hand in it. It could be improved if #10 bungs with holes suitable for pressure transfer were available,
May 26, 2021
over 3 years ago
Rated 4 out of 5
Awesome fermenter!
It's a great fermenter, plastic a bit soft.. sorta feels like a soda bottle... I do recommend to get the lid wrench with it. Cause it gets stuck. Basically it seals perfect just need help to open the lid.
January 29, 2021
over 3 years ago
Rated 5 out of 5
Great for Meads
I use these to make mead in. I wish they would have gallon marks on the fermonster. I just ended up adding my own.
Fermonster with gallon markings.
Fermonster with gallon markings.
November 10, 2020
over 3 years ago
Rated 5 out of 5
Much easier than a carboy!
Just completed my first ferment in this thing. Worked great! Large opening means I can pour in lots of grape bits and even drop (and later retrieve) some big chunks of oak.

Only one issue (which isn't big enough for me to give it fewer stars): wall thickness. It's super-thin so if you move the fermenter, just be prepared for the airlock to bubble out some liquid, or suck some back in once you set it down.
October 5, 2020
over 3 years ago
Rated 5 out of 5
Worked great did a elderberry wine. Do get the lid opener.
September 25, 2020
over 3 years ago
Rated 5 out of 5
Wide Mouth, Screw top w/seal
Great for small batches, test batches or if you are just getting started. Easy to clean & dry hop plus its harder to break than glass. Top does take a large than average plug (#10 is needed)
May 5, 2020
over 4 years ago
Rated 5 out of 5
Great upgrade from a 1 gallon carbon. Easy to use and prep. Have a gallon brewing now, hopefully easy to clean as well as prep for brewing
April 11, 2020
over 4 years ago