Introduction: How to Grow SLIME MOLD

Slime Molds such as Physarum Polycephalum can solve mazes and are said to be really smart. An article published in Scientific American explains How Brainless Slime Molds Redefine Intelligence. Slime molds are famous for their ability to form efficient networks between food sources that some say mimic road networks between cities. These organisms are often miscatagorized as fungi or bacterium but they are actually a single cell organism with multiple nuclei known as a protist and they are also extremely easy to cultivate at home!

We are going to test two things:

  1. Test what substances can be used to act as obstacles that the slime mold will need to navigate around on the agar plate. At the end we will contact an expert about unexpected results!
  2. How to capture video of slime mold growth. For this experiment I used an iPhone and a free app called Time-Lapse to capture footage of the slime mold's growth.

To grow your own SLIME MOLD you will need:

  • Physarum Polycephalum *You can easily buy this strain of slime mold on the internet. I purchase a "Living Plate" which will already have a good amount of slime mold growth on it by the time it is shipped to you. I bought mine here.
  • 100 mm diameter Petri dishes such as these.
  • Agar *Plain agar that is NOT fortified with nutrients such as sugar or beef stock is best. We want the slime mold to work for it's food. I picked up some from Amazon.
  • Oatmeal flakes from your local grocery store. You won't need more than a few flakes per dish.
  • Substances to test as a slime mold barrier. I will use Cayenne Pepper, Salt, and Triple Antibiotic.

Step 1: Prepare Your Agar Plates

Agar is a seaweed based gelatin that is used as the medium to grow microbes.

  1. Start by mixing 1 tablespoon of agar with one cup of COLD water in a small pot. (If the agar is mixed into the water after it is heated, the agar will clump together unevenly.)
  2. Once the agar is mixed into the the cold water bring the mixture to a boil and stir regularly.
  3. Fill each of your petri dishes with a thin layer of agar. Place the lids back on the petri dishes to minimize exposure to airborne microbes and let it solidify for 30-45 minutes.

Step 2: Create Barriers on the Agar Plates

I chose three substances that I think might repel slime mold growth.

  1. Salt
  2. Cayenne Pepper
  3. Triple Antibiotic

Hopefully, this will create barriers on the agar plate that the slime mold will need to navigate around to get to the second food source. The triple antibiotic was easy to squeeze on the agar. The salt and the cayenne pepper were made into a paste in order to apply them evenly onto the agar plates.

Step 3: Seed Your Agar Plates With SLIME MOLD.

Go ahead and open up the Physarum Polycephalum culture and transfer a small amount of it to your agar plates. Think about where you want the slime mold to start growing and where you will place the second food source that you want it to find.

Step 4: Add a Food Source

Place a few flakes of rolled oats directly on top of the slime mold culture. Next, place a few flakes of rolled oats on the other side of your barriers.

Slime mold does not like light so store your slime mold plates in a warm dark place.

Now let your slime mold grow and watch it in action!

Step 5: Day One

The Salt Plates

The slime mold has definitely started to devour it's local food source and its starting to spread out a little bit. Additionally, there seems to be a fuzzy unidentified organism also growing on the oats.

The Cayenne Plates

The slime mold on these plates also exhibit the fuzzy strands in addition to the slime mold growth. Strangely, they only appear on the the oats where the slime mold is growing.

The Triple Antibiotic

The slime mold has already found and made a connection with the second food source on the first plate from the left! The slime mold seems to be growing faster with the triple antibiotic than with the salt or cayenne pepper. These plates appear to have the least amount of fuzzies comparatively.

Step 6: Day Two

The Salt Plates

On day two these plates are getting more fuzzy and slime mold growth seems to be stunted.

The Cayenne Plates

These plates have also increased in fuzziness and the slime mold is spreading out slightly more than the salt plates.

The Triple Antibiotic

These plates again show the most slime mold growth and the least amount of fuzz. In the first plate, the connections between food sources has become thicker and the slime mold is branching out even more. Interestingly, the slime mold in the last plate appears to be growing over the triple antibiotic ointment in search of food!

Step 7: Day Three

On day three I placed each of the plates on a black background to better photograph the slime mold.

The Salt Plates

The growth of the slime mold and the unidentified fuzzes has slowed and it has not found it's way to the second food source on any of these plates.

The Cayenne Plates

The fuzzy organism is taking over these plates but the slime mold seems to be growing slowly regardless.

The Triple Antibiotic

These plates are still doing the best in growth. The slime mold on two of the three plates have connected to the second food source and they have the least amount of fuzzies.

Step 8: Day Four Conclusions

The Salt Plates

There are tons of fuzzies and the salt seems to dramatically inhibit slime mold growth.

The Cayenne Plates

These plates are still the winner for most fuzzies and the slime mold seems to be growing better than the salt. In the second plate the slime mold grew directly over the cayenne barriers to find the second food source!

The Triple Antibiotic

At this point it was no surprise that the plates with the triple antibiotic would do the best. It was able to grow around the ointment and directly over the ointment. The slime in these plates are growing so well that it is trying to leave the petri's time throw these away before they take over my apartment!


I wanted to know more about the fuzziness that was getting in the way of the slime mold so I sent an email along with some photographs to Steve Binkley at Carolina Biological Supply Company. He looked at the photos and quickly identified the hair-like strands as mycelial growth of a fungus. This means that there is a fungus growing in addition of the slime mold protozoa! Additionally, he speculated on why the plates with the triple antibiotic had little to no fungus growth: "It probably has to do with the nutritional requirements of the fungus. It is also possible that the antibiotics inhibit the fungal growth."

There you have it! We now know that slime mold cannot grow in salty environments and it will grow over and around pretty much any obstacle in it's way!

Step 9: Capture SLIME MOLD Growth on Video!

I wanted to a record time lapse video of the slime mold growth in action but I did not want to taint the salt-cayenne-antibiotic experiment and disrupt its growth in any way. I kept the agar plates for that experiment in a dark place with no light, which is its optimal growing condition, except for daily photographic documentation.

I am using a separate agar plate with no barriers because this video requires having light directly on the slime mold for a longer duration of time.

Try using a free iPhone app such as "Time-Lapse" to record the growth of this microorganism. I am setting the frame rate to 10 frames per minutes. This will give you about 600 frames an hour. I let app fun for 6 to 12 hours and these are the results that I received!