5 Reasons Compost Gets Slimy and How to Fix It

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Slimy Compost

Making compost can be a thrilling adventure. Compost supplies gardens with a nutrient-dense mixture that will help plants grow big and strong. Even though it may take a while to complete, it is worth the wait. Unfortunately, a few things can go wrong with compost if gardeners are not careful.

So, what are some reasons that compost gets slimy? Five major reasons exist as to why compost might start to get wet and slimy, which are:

  1. Too much water is added.
  2. The compost pile is not covered.
  3. Not enough carbon materials are present.
  4. Not enough nitrogen materials are present.
  5. The compost needs to be turned.

Compost should be checked often. If the next compost check shows that the compost is becoming slimy, then it is important to act quickly. While slimy compost can be a smelly, unsightly dilemma, the good news is that it’s typically a quick fix. This article will discuss why compost may becoming slimy and how to fix it.

The Top 5 Reasons Compost is Slimy and How to Fix It

Plenty can go wrong with compost, but one of the major problems gardeners find themselves running into is slime. Luckily, slimy compost piles aren’t the end of the world, or the end of the compost, for that matter. Read on to find the top 5 reasons why compost is turning slimy and how to combat the situation quickly.

1. Too much water is being added.

Slimy Compost

Does the Amount of Water Affect Compost Piles?,” by Shala Monroe, discusses the importance of water in a compost pile and how too little and too much water can cause major problems in compost. Water helps the decomposition process while also regulating the temperature of compost.

If too much water is being added to a compost pile, it will not be able to decompose properly, and the result will be a slimy, unsightly mess. All of this extra water is not necessary for the compost pile and can damage it in the end.

So how can one know if excessive water is the culprit of a slimy pile? Do a squeeze test. Put on a pair of gloves, grab a handful of the compost pile, and squeeze it. If water readily comes out from the pile, then far too much water is present. On the other hand, if the pile does not seem to have any moisture, then it is too dry – which can also cause problems.

The best way to combat slimy compost caused by adding too much water is to cut down on the amount of water you are giving your compost pile. Your pile should only have around 40 to 60% moisture at a time for proper decomposition.

In excessively dry climates, such as certain parts of Arizona and New Mexico, a bit of water might need to be added every day to keep the moisture levels appropriate. Those in wetter climates might find that they don’t need to water their compost piles much at all.

2. The compost pile is not covered.

Wet Compost

This goes hand-in-hand with problem number one. For those who live in an environment where there is an excessive amount of rainfall, compost will undoubtedly end up with too much moisture. This high amount of water in the compost will not allow for decomposition to take place, which will lead to a slimy heap.

Think about the area where you live. Is there a lot of rainfall? In many areas, the rainfall increases during the fall and winter seasons. Pay attention to the climate and the changes in the weather. Gardeners who live in an area where there is lots of rainfall need to cover their compost pile.

We have written an entire article on this topic if you are unsure if you should cover your compost pile. Should a Compost Bin Be Covered? Tips for Containing Compost

It isn’t just heavy rainfall that can cause problems, though. Proper drainage is also necessary if the compost bin is placed on a floor. Without proper drainage, no matter where a compost bin is placed, it will end up becoming too soggy if adequate drainage for the water added is not present.

Any compost that is left on the ground needs drainage. This can easily be done by providing a shallow trench that is dug away from the compost. Think of it as an irrigation system for the compost pile. This will help excessive water be able to drain and avoid the soggy situation.

If your compost pile is not placed in a low area that collects water easily, it will probably be fine as long as the pile sits directly on the ground. Never put a compost pile on a cement floor.

One additional tip – add larger branches and material to the bottom of the compost pile to help with drainage and airflow!

3. Not enough carbon materials are present.

Remember: the key to successful compost is a balanced mixture of carbon (brown) and nitrogen (green) materials. Without this balance, the compost is not going to work. One of the problems associated with a carbon/nitrogen imbalance is a soggy compost pile.

The best way to make sure that the balance is correct is always to follow the rule of one-third nitrogen materials mixed with two-thirds carbon materials. Take a look at the materials in your compost pile. Do you have the proper balance, or are too many nitrogen-rich ingredients present?

If a nitrogen-fueled compost is to blame for slimy compost, the problem is an easy fix. Just add some carbon materials to the compost pile, but make sure they are smaller pieces. Larger carbon materials will take an excessive amount of time to decompose, which won’t help the slimy problem anytime soon.

To learn more about carbon and nitrogen materials, the following chart gives more information.

MaterialCarbon or Nitrogen?Information
Wood ChipsCarbonHigh levels of carbon.
Tea LeavesNitrogenCan be used loose or still in the bag.
Food ScrapsNitrogenEggshells, fruit peels, etc.
StrawCarbonA good amount of carbon.
Shredded Paper/NewspaperCarbonDo not use anything with colored ink.
SeaweedNitrogenUse in thin layers.
Pine NeedlesCarbonUse moderately.
LeavesCarbonShred for easier decomposition.
WeedsNitrogenDon’t use seeds.
Grass ClippingsNitrogenUse in thin layers.
Dryer LintCarbonUse natural fibers.
Coffee GroundsNitrogenCoffee filters can be used, too.
CardboardCarbonShred before using.

Along with knowing what should be put into the compost bin, gardeners should also know what not to put in the compost bin. Items like meat, bones, and fish should never be applied to the compost. Also avoid perennial weeds, diseased plants, and pet manure.

When looking for the best materials to use to save a slimy compost pile, consider these carbon materials:

  • Lawn thatch. Thatch will add a hefty dose of carbon to the compost pile while also adding aeration, which is incredibly important for compost development.
  • Clean sawdust. Sawdust is extremely high in carbon, making it a great choice. However, it can bulk up and prevent aeration. When using sawdust, always make sure it is scattered to avoid clumping up.
  • Pine needles. Pine needles are small and can help with aeration. They are acidic, though, so consider tossing in some lime with the pine needles.
  • Peat moss. Peat moss does not provide any major carbon benefits, but the benefit it does provide is far greater. Peat moss can absorb excess moisture, which will bring slimy compost back to health.
  • Straw. Seed-free straw is a great option because it is an effective aerator while also adding carbon to the compost pile.
  • Leaves. Shredded leaves are another excellent option for adding carbon to the pile. Scatter the leaves so they do not become matted and reduce aeration of the compost.

4. Not enough nitrogen materials are present.

Sometimes, slimy compost can be kickstarted by activating it with nitrogen. It offers a quick and simple solution for any gardener that has noticed slime beginning to form on a compost heap. The best part is that this is one of the quickest and easiest options when it comes to recharging and rejuvenating soggy compost.

  • Option 1. Is any ‘completed’ compost available on the bottom of the pile? Toss this finished compost on top of the pile that is not completed. The finished compost will kickstart the other half, getting rid of the slime and bringing it up to speed.
  • Option 2. Don’t have any finished compost just yet? Toss in some garden topsoil to the compost pile, and it should work like magic.
  • Option 3. Lastly, if completed compost or topsoil is not ready to be used, opt for other types of nitrogen. Some of the most common ’nitrogen activators,’ as they are called, include blood meal, manure, alfalfa meal, and bonemeal.

Remember, do not add too much nitrogen material or more harm may be done than good. The proper balance should always be kept in mind when adding or removing any material to a compost pile. However, this nitrogen solution is a great way to fix slimy heaps and get back on track.

5. The Compost Needs to be Turned.

One important thing to remember when making compost is the compost pile must be turned fairly regularly (*if you want a fast, hot compost). This is especially true in the beginning when your materials are just beginning to decompose.

You can track the temperature of your compost pile with a compost thermometer. This is a good indication of when it needs to be turned, when the temperature reduces to under 100 degrees Fahrenheit.

Another indicator to turn your compost pile is when the pile reduces in size by one third.

If you are unsure about when and how to turn your compost pile, we have written a full article on this topic that you can check out here – When Should I Turn My Compost Pile?

Turning a compost pile is necessary for aeration. Aeration is important for a compost heap because it allows for the proper decomposition of materials. Without aeration, materials will just sit there. The materials will not be able to break down into the ‘black gold’ they are meant to be. This will eventually lead to a pile of slimy mess, which is exactly what we are trying to avoid.

The other problem with the lack of turning materials is that some materials can mat together and become clumpy. This stops the materials from being able to have the oxygen necessary to decompose properly. It can also hinder other materials from decomposing as they become a larger, matted mess that gets in the way.

To avoid potential matting, clumping up, and lack of aeration, always make sure to turn the compost pile regularly. Watch out for materials that are beginning to stick together and make sure to break them up. Gardeners can use their hands, their favorite gardening equipment, or they may consider purchasing a compost tumbler to turn compost piles.

Compost Tumbler Recommendations

Tumblers can be a great way to make sure a compost heap is being turned regularly. They are easy to use, and avoid the hassle of gardening tools to manually break apart materials and properly turn compost.

A good compost tumbler that doesn’t cost an arm and a leg is the FCMP Outdoor Tumbling Composter (Amazon Link). Some of its awesome features include:

  • Eight sided dual chamber.
  • Easy to use. Turn the tumbler every few days and have compost ready in as little as two weeks.
  • Large openings make it easy to add and remove scraps and materials when needed.
  • Two chambers allow two separate compost heaps to finish on their terms.
  • Excellent aeration thanks to the unique construction of the tumbler.
  • Extremely durable and BPA-free.
  • Less than $100.

Another great compost tumbler is the SQUEEZE master Large Compost Tumbler Bin (Amazon Link). Some of the impressive qualities of this tumbler include:

  • Easy to rotate.
  • An aeration system to allow oxygen in.
  • Dual chambers allow you to continue adding new material to one side while the other side finishes its composting.
  • Sturdy steel frame and BPA-free.
  • Made of high-quality recyclable PP.

These compost tumblers are a great choice for beginners and novice gardeners who want a quality heap of compost that doesn’t require too much work. The tumblers essentially do the bulk of the work themselves; all the gardener needs to do is add the materials and turn the tumbler. It truly does not get any easier than that!

Two Other Compost Problems and How to Fix Them

Slime isn’t the only issue to be concerned about when it comes to compost. Two other main issues are out there that gardeners are likely to deal with while making their compost.

Two other common compost problems are:

  • The compost smells bad. This is likely due to acidic problems. Compost should be slightly acidic, but too much of it is never a good thing. If the compost has an abundance of wet materials, the acid levels can begin to rise and cause an unpleasant odor to emit from the compost heap.

So, what can be done to make sure the acid levels are brought down to normal? If the compost has too much acid and is beginning to smell bad, simply toss in some lime or wood ash into the compost mix. Also add more brown materials to offset the amount of wetter green materials that are found in the pile

  • The compost is too dry. It is so important to make sure the compost isn’t too wet (otherwise slime and the inability to decompose occurs), but what about if a pile is too dry? If the compost is dry, it will stop decomposing. To fix this problem, wet the compost heap.

Remember, though, that the compost pile should be damp, not drenched. A gardening can filled with water and poured over the compost should be enough. Make sure to mix the compost heap generously to get all of the materials wet. At that point, decide if more water needs to be added or not.

Repent, then, and turn to God, so that your sins may be wiped out, that times of refreshing may come from the Lord

Acts 3:19


Nobody wants to see hard work and effort turn into a slimy, disgusting heap of materials. To be sure to avoid ending up with a soggy, slimy compost heap, make sure that there is not too much water, a proper balance of green and brown materials, and that the pile is being turned regularly. By following these simple tips, the chance of slime is reduced and a slimy compost pile can be returned to life.

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Corey Leichty

Hi, I’m Corey and I love using gardening as a way to provide food for my family, learn life lessons alongside my wife, Andrea, and teach life lessons to my two sons. Do you have gardening questions? Not finding what you are looking for? Please feel free to Ask a Question (Click Here!) and I will get back with you as soon as I can!

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