FerMonster 7 Gallon Carboy

FerMonster 7 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, and still sells for less than $30. 

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 smooth ribless walls are a feature that reduces yeast and sediment buildup, and imbedded are volume markers at five, six, and 7 gallons.  The huge 4" opening makes filling a breeze, and cleanup is as easy as wiping down the inside.  The 7 gallon is a monster of a fermenter, reducing blowoff issues seen with standard carboys.  Glass carboys are fragile, and this is nothing like that.  The hefty plastic construction will hold up to brew day abuse; and while movement is manageable, these can be upgraded with our Carboy Carrier.

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 impermeable to Oxygen penetration
  • Volume Markers at 5, 6, and 7 Gallons
  • 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: 20.9 inches
  • Diameter: 11.3 inches
  • Completely taste and odor free
  • Perfect for Beer, Wine, Cider, Mead, Kombucha or any other fermented beverage!
  • Thick walls for better oxygen barrier.
Item # FE255
Shipping Eligible for Free Shipping Program
Availability California - In Stock
Pennsylvania - In Stock
Weight 3 LBS
Community Q&A

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What is the diameter of the opening in the fermonster? not the lid but the body itself.
Aaron Linder on Apr 13, 2020
BEST ANSWER: The opening of the mouth of the carboy is 4" wide.

3.9 / 5.0
17 Reviews
5 Stars
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1 Star
Rated 5 out of 5
Great carboy
I have a few of these and love them! I have seen a lot of negative reviews and can’t figure out why unless they are not being used properly. Mine seal up great every time, all the time. They are lite and easy to carry with 5-6 gallons of liquid. I’m 6’2’& 240lbs and though it’s really tight, I can get my arm inside for a through cleaning with soap and a soft cloth. The O ring is larger that the lid. It takes a little work to get it in the track. Once you figure it out and get it, it’s great. There is a YouTube video for those of y’all having problems. As for the stopper. If you have one of the cheap, hard rubber #10 stopper, you will not get a good seal! Morebeer offers a few different stoppers in this size. The one you can add as an option is the softer rubber wine stopper thyat works with this hole. As I said, I’m a pretty good size guy and I have had difficulty opening the lid at times after fermentation. I was at large homebrew store in Austin Texas and I saw they had a Fermonster lid opener. It was like $5 and I bought it, super good tool to have on hand. If you’re not sure after reading a few of the negative reviews, don’t be afraid. These work excellent if you use them correctly.
August 16, 2019
Rated 4 out of 5
works well, with some tricks
I like mine, way easier to move around than the glass carboys, and safer. I'm probably about 10 brews in on it at this point and it shows no signs of wear anywhere.

As others note, the lid can be tricky. You have to tighten it quite firmly to get a proper seal. Then, because the lid is so big its hard to get a good grip on it by hand to loosen it. My solution is to use a big woodworking clamp like an oversized wrench (I have 48" ones in my shop). I grab the lid with that and it twists off super easy - leverage FTW. Sounds like they've created a special tool that basically does the same thing now.

If they redesign anything, it should be the inside of the lid. The o-ring is too thin for the large diameter of the lid. They need to make the o-ring thicker (like you find on the inside of a keg for example) so its easier to get a seal AND so its harder to distort the o-ring while you're installing it.

At any rate, the price point was good for me, and I'm making it work for my purposes just fine. The extra head space is great, no more blow off tubes for me!
July 14, 2018
Rated 3 out of 5
Be Careful for Wine Storage
I noted from the reviews that most people use this product for beer. I bought two to replace some old and very heavy 7 gallon glass bottles, mainly for storing wine between fermentation and bottling. Seven gallons is too small to be a primary wine fermentor.
The problem with storing wine in this product is that the large top creates a large place for air to sit on top of the wine and cause spoilage. The level in all wine storage vessels will change with even a modest change in temperature. So if filled to the brim in September, by November when the cellar temp has dropped, there can be a 1/4 inch air gap. If that gap is topped up to the brim again, it will overflow when the temp warms up in the spring. One so-so solution is to place a sheet of food plastic wrap loosely over the wine and carefully screw the top on so as not to rip the plastic.

If you are having trouble unscrewing the top, buy a strapping wrench. It's a handy tool to have around.
July 9, 2018
Rated 3 out of 5
Great product, just some things to consider
I like the wide mouth which is good for adding fruits and other things without trying to shove it in. The only issue I have is that the O ring is slightly larger than the seat so much so that it doesn't fit right inside the lid that you don't get a good seal. I just had the O ring fall into my chilled wort, lucky thing it was sanitized (I didn't even bother fishing it out since it fell to the bottom). Lastly, (more of a caution) if you ferment outside an enclose fermenter, there is a possibility of mold/dust/bugs, etc. growing inside the spigot, so I always use a siphon now.
May 24, 2018
Rated 5 out of 5
Very easy to use and easy to clean. Sometimes lid is hard to remove but does not take away from quality and ease. I plan to plan to buy another.
March 29, 2018
Rated 5 out of 5
My best fermenter
Over the last 9 years of brewing, I have gone from glass to plastic fermenters. Have a number of better bottles which work well, but cleaning can be a pain at times and a blow off tube is necessary on almost all ales. Have a Spieidel which I like and the built in handles work well plus is large enough to not need a blow off, but have continued to have problems with leaking from the spigot. The Fermonster has solved those problems. No need for a blow off tube, and cleaning is a snap. The sprayer on the sink gets most of the crud off, and I use a microfiber cloth and PBW. I feel better being able to scrub the inside rather than just letting the PBW soak. I use a Brew Hauler strap which works great. The gallon markers on the outside are difficult to see, so I outlined them with a Sharpie and that helps a bunch. The only downside is the seal on the lid. The O ring is properly seated, but sometimes it works and sometimes not. No big deal as it does not affect the fermentation. Have seen on the manufacturers website a handle for tightening and loosening the lid, but have not found it on More Beer or anywhere else.
Overall, satisfied with these and feel they are the best option out there.
August 27, 2017
Rated 1 out of 5
Only lasted five brews!
Glass carboys, no problem, I've lost track of how many brews. FerMonster...lasted five brews before the bottom cracked (never miss-handled or dropped it) and it leaked out into my fermentation fridge. I was able to save about half of the brew by transferring into a glass carboy. Cheaply made product, I highly recommend NOT buying. Stick with glass or stainless, or even buckets!
August 9, 2017
Rated 5 out of 5
Fantastic upgrade
I purchased 4 of these to replace the buckets I had been using for the last 7 years. The 7 gallon size is perfect for 6 gallon batches with enough headspace for the krausen. The markings are accurate. As others have said, the lid can be very difficult to get off when you put it on too tight. I have found that barely hand tight is enough to get a seal with the o-ring without requiring hulk hands to remove it. The large opening is fantastic for everything from pitching yeast and dry hopping to cleaning and drying. For the price, this fermenter can't be beat.
May 23, 2017
Rated 2 out of 5
Not a Fan...
I've been using a Speidel over the past year and have been very pleased with the extra head space and the durability. I was hoping for the same with the FerMonster, but it's just not there. It feels cheap like I'm holding onto a an empty two liter bottle, the measurement marker is not accurate, the rubber gasket doesn't fit to create a seal, and the cap cracked on only the second time using it for a primary. I'll stick with Speidel fermenters from now on.
May 21, 2017
Rated 4 out of 5
Great fermenter.
So I picked one of these up a while back and have brewed a few batches with it and I am impressed.
It's plastic, so no worries about dropping it and bleeding out. Smooth sides make for easy cleaning. The punted bottom really does make siphoning out clear beer much easier. Good seal on the lid, haven't had any problems with it.
My only downside to this is the side of the opening. Yes, it's much larger than a regular carboy but it could be a wee bit bigger. I'm not a "sun's out, guns out" person but my arm is a bit bigger than the opening. I can still reach the bottom and clean this with a cloth but I have to jam my arm in. If you're a pro cyclist with those skinny T-Rex arms, this will be perfect.

All in all, I'm super happy with this thing and wouldn't hesitate to recommend it.
January 29, 2017