Can Sphagnum Moss Grow Underwater? Sphagnum moss is a type of moss that is commonly found in wet bogs and swampy areas. This moss is known for holding large amounts of water, making it an ideal plant to use in gardens and landscaping.

However, due to its high level of water retention, many people are curious as to whether or not sphagnum moss can grow underwater?

Sphagnum moss can technically grow in water, “but” it’s important to note that only the moss on top will survive! If the moss is completely submerged, it will start to decompose.

In fact, sphagnum moss is often harvested from bogs and swamps for its decomposed parts below the water’s surface known as peat moss.

Peat moss forms when the decomposing plant matter accumulates underwater. Over time, the decomposed parts of the moss will build up and create a layer of peat.

Why Can’t Sphagnum Moss Grow Underwater?

Although sphagnum moss has the ability to soak up more than eight times its own weight in water, it cannot grow completely submerged and there is a good reason for this! The answer has to do with the structure of the plant itself.

If sphagnum moss is completely submerged underwater it will cause the following:

Hyaline cells will fill up with water and rupture
The leaves can’t photosynthesize properly
Water prevents the plant from absorbing oxygen
The moss is unable to absorb the light

Sphagnum moss is composed of single-layered leaves that have two kinds of cells hyaline cells and tiny green photosynthetic cells.

The hyaline cells absorb water from the surrounding environment and the photosynthetic cells are located on the surface of the leaves and are responsible for producing food for the plant.

Take Note: If sphagnum moss is completely submerged, the hyaline cells will fill up with water and rupture. This will damage the plant and prevent it from being able to photosynthesize properly. In turn, this will cause the plant to die.

Being underwater will also prevent oxygen from entering the plant. Without oxygen, sphagnum moss would be unable to carry out cellular respiration a process that is essential for the plant to grow and thrive.

While other aquatic plants are able to get the oxygen they need which is dissolved in water, sphagnum moss does not have this ability. As a result, it is not able to grow underwater.

Additionally, sphagnum moss also needs parcel light in order to grow. If the plant is completely submerged, it will not be able to absorb the light it needs to survive.

How Long Can Sphagnum Moss Last Underwater?

When sphagnum moss is submerged in water, it only survives for 2 to 3 days any longer and the moss will start to break down and release tannins into the water.

Tannins are a type of organic compound the peat moss releases which can cause the water to become stained and discolored.

Too much tannin in the water can also be harmful to fish, as it can lower the oxygen levels in the water and make it harder for them to breathe.

For these reasons, it is not recommended to keep sphagnum moss submerged for long periods of time.

Can Sphagnum Moss Be Used In Aquariums?

Yes, you can use sphagnum moss in an aquarium, usually on an object, that’s partially out of the water. However, there are a few things to keep in mind. First of all, sphagnum moss will alter the water chemistry of your aquarium.

The exact changes will depend on the type of sphagnum moss you use and the conditions of your aquarium, but because peat moss releases tannins you can expect the pH level to decrease and the water hardness to increase.

Because of this, it’s important to test the water regularly and make sure that the levels are still within the acceptable range for your fish.

Additionally, you may need to adjust your filtration system to compensate for the changes in water chemistry. Another thing to keep in mind is that sphagnum moss can be a bit messy.

When it breaks down, it releases small pieces of itself into the water column. These pieces can clog filters and cause other problems, so it’s important to clean them out regularly.

Final Thoughts

So there you have it! Now you know that Sphagnum Moss can’t survive for long periods of time when submerged in water. While it can be used in aquariums, there are risks.

If you want to add moss to your aquarium your best option would be to use underwater moss like java moss which doesn’t release tannins like sphagnum moss does.