Fermonster 1 Gallon Carboy

Fermonster 1 Gallon Carboy

Accessories for your Fermonster  
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Carboys are great, but they have some issues: They require funnels to get liquid in, and cleaning brushes to clean up after.  They hold a decent volume, but all are a bit undersized for fermentation, and have no inherent measuring system.  Glass Carboys are breakable, while plastic carboys scratch with the first brush cleaning.  The Fermonster leaves all these problems behind!

These Fermonster Plastic Carboy Fermenters are made from heavy PET plastic, the same used in 2 L soda bottles, which is nearly impermeable to oxygen penetration. The huge 4" opening makes filling a breeze, and cleanup is as easy as wiping down the inside. Glass carboys are fragile, and this is nothing like that.  The hefty plastic construction will hold up to brew day abuse.

These fermentors are completely air-tight; the bodies constructed of heavy, oxygen impervious P.E.T. plastic, 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: 0.6 lbs
  • Temperature Limit: 140° F
  • Height: 9.45 inches
  • Diameter: 6.7 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 # FE259
Shipping Eligible for Free Shipping Program
Availability California - In Stock
Pennsylvania - In Stock
Weight 0.59 LBS
Community Q&A

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Browse 2 questions Browse 2 questions and 4 answers
Why did you choose this?
MoreFlavor Store
Perfect size for my 1 gallon batches.
Calvin N on Aug 12, 2022
Wanted to compare a quality plastic car it against glass.
Ryan R on Feb 26, 2022
Perfect size for my 1 gallon batches.
Calvin N on Aug 12, 2022
Small batch making
Joseph R on Apr 6, 2022
Wanted to compare a quality plastic car it against glass.
Ryan R on Feb 26, 2022
For fermenting small experimental batches of beer and kombucha.
Jonathan B on Nov 30, 2021
Experimental beers or beers that I’ve never tried
Chad G on Sep 13, 2021
Need another
Randy R on Aug 17, 2021
Perfect size for small batch ferments
Chris K on Apr 2, 2021
Small brew operation
Lori Lyn G on Dec 29, 2020
Perfect size and not glass
Arnie L on Dec 21, 2020
Small batch of watermelon wine
Russell M on Nov 16, 2020
i brew gallon batches
keith k. on Oct 10, 2020
Anticipating extra wine pressing capacity
KUEHN C on Sep 23, 2020
To do small-batch experiments.
Charles E Hammond on Jun 9, 2020
I wanted to have two or three small, one gallon carboys on hand while making wine and I didn’t want to use glass jugs.
Keith on Sep 10, 2019
small batch cider and mead
Donald T F on Jul 5, 2019
Yeast store age
Jason Fuller on Apr 29, 2019
small batch secondary fermenter
Kenneth C on Mar 4, 2019
Based on reviews and research this looked like the best option for small batch fermenting for my use.
Rodney H on Jan 29, 2019
Upgrading my small batch brewery
hnnrrk on Jan 13, 2019
Best fermenter for 1 gallon wines and meads
Steven McPeak on Aug 8, 2018
Easier than glass jug
Steven McPeak on Jul 31, 2018
trying out a plastic one gallon carboy
Sal Coco on May 1, 2018
Small batch making
Joseph R on Apr 6, 2022
For fermenting small experimental batches of beer and kombucha.
Jonathan B on Nov 30, 2021
how many litres does this hold? Is it 4.5l or the US gallon of 3.78?
Ciaran Walshe on Mar 20, 2023
BEST ANSWER: It's a US gallon. I haven't measured it exactly, but it's obviously smaller than my UK 4.5L demijohns.
What size stopper needed?
Jonathan Manatt on Apr 14, 2018
BEST ANSWER: The Fermonster 1 gal. takes a #10 stopper.

4.2 / 5.0
9 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star
Rated 5 out of 5
Perfect for small batches
The perfect size especially the top section for brewing small test batches works great!!
December 24, 2021
over 2 years ago
Rated 5 out of 5
Nice to be able to see primary fermentation
The Fermonster is superior to using a white plastic fermentation bucket with a solid white lid. The Fermonster seals well so that the airlock is the only way for the C02 to escape. Between monitoring the gas escaping from the airlock and a visualization of the clear plastic tub, a far better determination of the state of the primary fermentation can be made with the Fermonster. The stopper is a must have accessory. (pun intended) and an extra gasket plus a solid lid helps when it comes time to degassing.
March 2, 2021
over 3 years ago
Rated 3 out of 5
Very small Wish i went with the 3 gallon
January 28, 2021
over 3 years ago
Rated 4 out of 5
super convenient, easy to clean. great for split batches or small experimental batches.
January 25, 2021
over 3 years ago
Rated 5 out of 5
Straight forward and versatile.
Works well. Easy to clean. A no frills car boy that performs as expected. Sidewalls are very thin and I expect they would not hold up well in hot water.
Used to ferment kombucha and vegetables.
November 27, 2020
over 3 years ago
Rated 5 out of 5
The coffee drinker in the House loves it!
I bought this to make it easier for my wife to do larger batches of cold brew coffee. 12oz coffee and 3 qts of water and in the fridge it goes. She loves it.
August 26, 2020
over 3 years ago
Rated 3 out of 5
Not as high quality as expected
* Lightweight!
* Won't shatter like glass.
* Large mouth makes cleaning a piece of cake.
* Slightly larger than 1 gallon, so I can actually bottle nearly that much.

* As many have said, the thin walls make me feel like I'm going to collapse or dent it.
* The o-ring provided for the lid doesn't stay on. Pretty sure it's going to fall into my beer, so I threw it away. It keeps a seal without it anyway.
* The dent where the spigot might go is annoying and unnecessary (I'm never putting a spigot on it).
* The larger-than-normal stopper required is not easy to find. I ended up fabricating a 2-hole of the right size and did not enjoy the experience.
September 6, 2019
over 5 years ago
Rated 5 out of 5
Mixed up a 1 gallon batch of Blackberry Mead. The shape and wide mouth opening is perfect for degassing and adding nutrients. Much lighter than glass without the danger of dropping and breaking. Easier to clean than a gallon jug. I like the wide opening for the bung too, don't have to unscrew the lid to take a reading or add to the batch.
August 5, 2018
over 5 years ago
Rated 3 out of 5
Pretty thin plastic
I got my 1 gallon Fermonster in today. I have four of the 6 gallon versions and love them. The 1 gallon versions aren't as thick and flex very easy like a cheap water bottle. I'll do an update after a few uses, but my first impressions aren't looking to great.
July 20, 2018