Algae or Biofilm? What’s the Difference?

Published Jan 26, 2021

As you progress on your Gardyn journey, you might notice some brown or green growth forming on the yCube surface, yPod, or inside the Gardyn columns. Typically, this growth is associated with algae or biofilm.



Algae growth typically manifests as green buildup on the yCube surface or inside the column. It forms when water and plant food access light on the surface of the rockwool. Algae is identified by a green growth, dark or light, but it doesn’t carry any odor. While many people become alarmed by algae, it absolutely isn’t harmful to you or your plants.

The main thing to look out for with algae is when the plant is first establishing. If algae takes over the yCube before the plant has time to push its roots into the pod, it’s possible for the algae to out-compete the seedling for nutrients and starve it. In most cases, seedlings will establish before algae has time to take over. If you have a seedling that’s struggling, take a look at our algae remediation tips in the Resources section of your Gardyn App.

Cousins to your plants, algae uses water, nutrients, and light to photosynthesize their energy. It can clean your air over time and even provide your home with extra oxygen! Algae isn’t an issue in hydroponics because hydroponic plants are constantly provided with fresh water and nutrients, where algae in soil is competing with the plant for the limited nutrients available. If you see algae forming on your yCubes, say hello! Algae is a friend, not a foe.


Biofilm is distinguished from algae by its color and location. Biofilm is typically a caramel or brown color, and grows on the inside of the pods or inside of the columns. It’s not uncommon for biofilm to make its way down into your tank over time too, which is one reason why it’s important to clean your tank regularly. 

Biofilm is a natural byproduct of plants growing, whether in soil or hydroponics. Plants have evolved to foster a symbiotic relationship with microbes and fungi that live in soils. In nature, these fungi will break down organic matter into available nutrients for the plant. In exchange, the plant will release carbohydrates through its roots, called exudates, to feed the good fungi and bacteria. 

Just because we’re growing in hydroponics, doesn’t stop the plants from exuding this food to attract beneficial microbes. These circulate through the water and will feed bacteria and fungi that exist everywhere and have found themselves in your Gardyn.

Over time, these populations can grow into Biofilm and start to be visible. It’s important to clean the tank and system regularly to keep biofilm populations under control. It can also be a good idea to periodically add H2O2 to the system to nip any colonies in the bud before they can become a problem.

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