Growing Bigger Worms

Here is a question from Wade:

Bentley, I currently have red wigglers, european night crawlers, african night crawlers and alabama jumpers.
My favorite are the red wigglers cause they are a better size to fish with, the others grow too big for my hook.
I have noticed in raising my red wigglers, I have plenty of them but they just won’t get very large, maybe 1 inch long. What am I doing wrong, I have just built a large 4ft x 8 ft x 12 inche bin for them in hopes that they were just crowded. I have rabbit manure in there and also feed them fermented vegetable scraps in hopes they will grow by fishing season.


Hi Wade,
This is a fairly common scenario. Red Worms are quite small in general, but 1 inch would definitely be below the adult average (likely more like 3 inches). There are two main factors that seem to play a role: 1) Nutrition, and 2) Moisture content.

The absolute BIGGEST Red Worms I’ve seen (more like 4 or 5 inches) were living in various old outdoor manure (horse manure + stall bedding) heaps. This habitat/food is clearly top notch for these worms since this is also where I’ve seen some pretty amazing densities as well (although I’ve had pretty good luck in my own systems too).

Often, when worms get really crowded food resources can end up in shorter supply, however, thus limiting the amount of nutrition that each worm can get (likely other factors that come into play with crowding as well). I’ve certainly had plenty of systems that were loaded with worms where the average size seemed to be on the small side.

Moisture content can be another really significant factor. Worms are basically little semi-permeable bags of water, so as the surrounding environment dries out they too lose moisture and thus body volume. I’ve noticed in less-than-ideal enclosed plastic bin systems that worms can remain quite plump in comparison to those in open (especially outdoor) systems that are actually operating more efficiently (better overall worm health etc etc).

If you can provide your worms with sufficient moisture (still best to use systems with good drainage and/or air flow if at all possible), rich food materials (such as manure, “worm chow” etc) and a bit more space to spread out in you should see an increase in size for sure. Just be careful with “too much” moisture (usually only an issue in systems that don’t drain) and “too much” nitrogen – the latter can result in ammonia release (deadly) and a condition known as “protein poisoning”.

Your new system sounds great – just make sure you also have LOTS of bedding materials in there as well – it will help to balance the C:N ratio and will provide the worms with a lot more habitat value (bedding air flow, space etc).

Anyway – hope this helps, Wade! I’m sure other folks will have their own nifty methods for growing fat worms as well – hopefully some of them will share here!
Thanks for the great question.

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    • Steve L.
    • February 14, 2011

    Here’s some observations from my bins. I’ve never made an effort to grow the worms bigger… yet. 🙂

    My smallest EF’s are in a plastic barrel FT that’s been running about 4 months now with shredded leaves as the primary bedding material, and resides in a shed. My largest EF’s are in a 4 foot diameter compost pile contained by a ring of steel fencing that is outside. There were so many worms in the material after I’d hot composted the pile that I thought I’d just start feeding them on top with a thick layer of whole leaves. This “bin” is also about 5 months old.

    Why are the outside EF’s bigger? I do feed them more, but less frequently, and they do have more bedding on top of them; the wet leaves also insulate them from the winter air, so it’s up to 2′ thick with leaves at times. I think the indoor bin is denser with worms per sq. ft.

    Another difference, but I doubt is a reason, is that the bedding of the bin in the shed stays between 57 – 80 degrees (avg. 65-ish) due to the bin being insulated and I feed them so as to generate heat, and the outdoor pile has been 50-60 in January.

    I’ve wondered if underfeeding and shredded leaf bedding is a factor for the smaller worms in the FT.

    • Laura
    • February 22, 2011

    Are worms measured when they’re stretched out or when they’re thick? (My worms would either be approx. 2-3 inches or 4-6 inches).

    • Julie
    • March 4, 2011

    I’m wondering the same as Laura. I’ve noticed some tiny thin and small worms, and other worms stretching out to 3 or 4 inches, but then they get very skinny , amazingly thin (I can’t see trying to put them on a fish hook for example)

    I’ve yet to see a really thick and “big” worm though.

    so, when people describe their worms, in what state of stretchiness are they? 😉

    • BassBuster
    • July 27, 2011

    I have a large outside compost bin approximately 4x10x4′ tall. I compost large amounts of fall leaves. I actually bag them in plastic contractor bags turn them upside down to keep dry and store them (from several friends) and add them to the pile during the summer with grass clippings. Contrary to what you hear most of the time red worms prefer grass clippings. Clippings hold plenty of moisture and ferment quickly. Temps over 100 degrees don’t even stop them. They don’t grow as large in grass clippings but to maintain a better pile I mix 50% green/50%brown. For brown I prefer fall leaves. OLD horsemanure/wood shreddings counts, newspaper, cardboard, straw….but the main secret is the pile should be bottomless for drainage and the pile will work incredibly well if you have a good source of declorinated water to keep it moist. In the past I operated 100 aquariums and did water changes of 500 gallons a week…all pumped onto my compost pile year round. The worms…both redworms and canadian crawlers grew HUGE. So called Canadians were up to 12″ long and reds were big but not monsters. I suspect reds are graded constantly and larger ones sorted out and put into new beds constantly so there is no competition for food. I am currently experimenting with making alfalfa meal/oatmeal jello’s. I am wondering if making jello will hold moisture better. My guess is this will be unsuccessful as the worms feed on the surface decomp not the “food”. I’ve heard that chick starter is the primary food for many commercial operations. The only reason I haven’t tried it is I use reds for fishing for gills and I use a tiny hook (don’t even know the number) just so small I have trouble seeing the hole to tie it. I use 5# braided line and this tiny hook so almost any red will work. I often catch 2-3 lb bass on nothing more than a 1″ redworm and this tiny setup. 2-3 lb bass on ULTR ULTRA lite is a blast. If you have a relatively small pile leave on side open and place a piece of cardboard on top insulated with styrofoam to keep it cool/moisture in. Chlorinatewater will work but it slows decomp down some.

    • Joon Siu
    • March 16, 2013


    I’m looking for a breed of worms that has the most prolific growth rate and speed for gaining biomass. I’m working on a proposal application for industry & university collaboration research grant from a Government fund; research topic is on the extraction of active proteins from earthworm bodies.
    We’ve found the global favorite of eisenia fetidia to be substandard of the requirements we need due to their small bodymass (although they do have great efficiency). Anyone with ideas on this, please help.

    Furthermore, if this application is accepted, we will be looking for a worm consultant.


    Joon Siu.

    • T.K.
    • September 23, 2014

    I know this is an old article but I just want to put in my two cents. I gave my in-laws a worm composting bin for this past Christmas so they could use them for fishing (they go often and their closest “bait” shop is Wal-Mart, yuck!).

    I kept up with them for awhile before giving it to them. They just weren’t thriving like I had hoped. It is even more difficult, seemingly, living in Texas and trying to produce the best possible worm. Nothing seemed to work well.

    My last visit with them about a month ago I notice he was feeding them oatmeal. Those suckers were so plump – perfect for fishing. So if anyone out there is looking to fatten them up, OATMEAL is the way to go.

    • shannon
    • December 28, 2015

    I have the opposite issue, very large worms that do not seem to multiply. Any advice as to how I can encourage worm population growth?

    • Bentley
    • January 7, 2016

    Hi Shannon,
    What kind of worms are they and where did you buy them? Certain species are definitely NOT well suited for life in a typical worm bin/bed.

    • shannon
    • January 12, 2016

    Hi Bentley,
    Thanks for your response! I bought “Red Wigglers” from a reputable source, they have the little dark red splotches on them. I intermittently put them outside when it’s warm enough, but it is still quite cold where I live (~5 to -5 degrees Celsius roughly). Do you have any idea of causes? Or potential solutions? Or do you know more about the life cycle of Red Wigglers and perhaps they are just in the growing stage? Maybe I’m overfeeding them?
    They seems to be enjoying the bin, I’ve heard that natural Earth worms will not survive in a bin – so that’s all I’m basing it on.
    Any help at all is appreciated!

  1. Could shed pet hair be used in a composter for the base?

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