Lime For Worm Farm – How Much to Add & the Different Types

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Are you new to owning composting worms or are you a seasoned veteran?

You’ve likely come here because you have questions about composting worms and the use of lime to create a healthy worm bin environment with a more neutral pH.

Perhaps you’ve heard from other worm owners that they use lime to keep their colony happy or you’ve heard comments against the use of lime.

It can be very confusing, but it’s important to get a better understanding of using lime with composting worms because while it can be helpful if you choose the right lime, it can also cause problems if you choose the wrong lime.

What Does Adding Lime to Your Worm Farm Do?

First and foremost, you will probably be wondering why on earth you may want to add lime to a worm bin in the first place.

Surely, they are self-sufficient and as long as you keep the conditions right, they will be fine?

Well, yes ideally, but let us explain why lime may be helpful.

Adding lime to worm farms offers two benefits:

  • Helps to keep your worms happy by keeping the pH of the soil balanced so that it is not too acidic
  • By providing them with additional calcium

Should I Add Lime to My Worm Farm?

Even without doing any tests, you can often tell if you need to add some lime to your worm farm if your worms are happy or not.

How can you tell if your worms are happy?

One of the clearest signs of unhappy worms is if they are trying to escape your farm.

If they are trying to escape it could be because they do not feel they are getting the nutrients they need or that the environment is not as comfortable for them.

Investing in a pH meter or pH strips should also help tell you whether there are acidic conditions in your worm bin.

What Kind of Lime Do You Use in A Worm Farm?

You need to be careful with the type of lime you add to your worm farm as there are a lot of different options out there and while the right choice of lime will help your worms thrive, the wrong choice can harm them.

You want to avoid:

  • slaked lime
  • builders’ lime
  • hydrated lime

These are highly caustic and not in the least bit worm-friendly.  

Ideally, the type of lime you want to use in your worm farm has a CaCO3 of 95% or even higher.

Dolomite Lime, however, is one exception to this rule as that has a 50:50 ratio of MgCO3 and CaCO3, so it is perfectly fine for your worms or your garden.

How Much Lime Do You Put in A Worm Farm?

Of course, before you add any lime to your worm bin, you need to know how much lime to add to worm farm.

Here are a few strategies:

The first thing you need to note is that you don’t need to use a large volume of lime when you are trying to keep your worm farm thriving and productive.

Everything in moderation, and this is no exception, especially if it’s a first test.

  • Generally speaking, unless there are ongoing issues, you only need to give your red wigglers a handful (or for something more exact, ¼ to ½ a cup) every fortnight. 
  • Depending on your setup, it may be a good idea to create a shaker container to lightly dust the soil with lime to keep your composting worms happy.
  • Another thing you need to keep in mind is how moist or dry the soil is in your compost.

If the surface and inner soil is moist to touch you don’t necessarily need to water the dolomite lime or whatever lime you choose to use into the soil.

However, if it is a little dry, it may be a good idea to sprinkle some water over the area to moisten it before you work it into the rest pile.

Red wigglers are often very sensitive to the surfaces they travel over and if they come across dry particles it may not be pleasant for them.

This is why it is essential to grind egg shells into a fine powder in case you start causing problems or harming your earthworms.

Does Lime Affect Worms?

Again, as we have already highlighted, there are several different materials and substances out there that bear the name lime.

You need to be careful to choose the right one.

Some can greatly impede the productivity and even life of your compost worms.

While others, like Dolomite Lime, to name one of the most popular, can help to keep your worm farm healthy with a balanced pH. 

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Is Dolomite Lime Safe for Worms?

Dolomite lime is a form of agricultural lime and can help balance the acidity levels in soil or compost.

With that in mind, as we have already considered, Dolomite lime is ideal.

Compost worms tend to thrive and enjoy the most comfortable living conditions when the pH ranges from 6.5 to 7.

Dolomite lime can help you achieve that number.

Is Dolomite Good for Worm Farm?

Dolomite lime, in powder form, is the perfect addition to your worm farm.

It’s safe and helps to keep the acidic levels of any soil it is shaken over and worked into down and balanced. 

As with everything, large amounts of something can end up being a bad thing, so go slow.

Do Worms Like Dolomite Lime?

It is crucial to make this point that carefully chosen lime mixed into the worm bed or worm bin can help keep your worms happy and encourage your worm farm to perform the function you invested in it for.

Does that mean they should always have it?

Not necessarily, no.

Most of the time a vermicomposting colony of red wiggler worms can survive quite happily without the addition of dolomite lime or another type of agricultural lime.


So, whether you are completely new to composting worms and worm farming and have read about using limes or are looking to improve the productivity and quality of life of your existing worm bin, lime can help.

Make sure you are careful to check the pH levels of your worm bin before you start adding lime, though, and be sure to only add the lime we have outlined above.

Avoid anything too caustic that may hurt your worms, and even break their skin, causing them to die.

Stick to Dolomite lime.

Even if you just do it as a nice treat for the inhabitants of your worm bin, they will be more than likely happy and appreciate of you looking after their environment.

Keep feeding them with the foods they love while doing this treatment like fruit, greens, plants, and other food or kitchen scraps like coffee grounds.

Keep balancing it out with browns like cardboard, paper etc for their bedding and you’ll keep your little buddies happy.

Never stop their feed while going through this treatment. Your worm farms should return to a healthy environment soon.

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