Putting oak leaves into your aquarium is a great way to increase the water tannin levels and provide food for shrimp and snails, especially when setting up a new tank. Tannins are acids that occur naturally during the decaying process of wood, wood bark, leaves, alder cones, etc.

Tannins are proven to prevent bacteria growth and reduce inflammation and are therefore often used in blackwater aquariums. Before adding them, it is important to remember that a high concentration of tannins in the water usually causes a brown or yellow tint.

To prepare oak leaves for the aquarium is it best to boil the oak leaves and add to the aquarium when the water has cooled down to room or aquarium water temperature.

Step 1: Acquiring oak leaves for your aquarium

Depending on where you live, you can either collect your oak leaves or buy them in your local fish store or online.

When collecting the leaves yourself, make sure to choose relatively clean looking leaves that are free of rot or mold in order not to introduce unwanted substances into your tank.

It is important to use dried leaves instead of fresh ones, otherwise they may not sink to the ground.

When buying the Oak Leaves in a store or online you can usually get plastic bags of clean and dry leaves in different sizes and weights.

Two to three leaves are usually enough for a nano tank but you can also use a bit more in bigger tanks or when planning a blackwater aquarium.

Step 2: Preparing the oak leaves by boiling them

Place your dried oak leaves in a cup or bowl and fill it with boiling hot water until the leaves are fully covered. If the stalks tend to rise above water level you can use a fork or spoon to weigh them down.

Now leave the oak leaves in the cup or bowl until the water has reached room temperature or for a couple of hours before adding them to your aquarium. Adding hot water to your aquarium will tamper with your water temperature and might harm your aquatic animals.

After a while you will see that the color of the water in the cup will turn brown or yellow. This is a good sign as tannins are being released to the water, which will be beneficial to your aquatic animals.

Oak leaves in a cup and covered with boiling water Oak leaves in a cup and covered with boiling water

Step 3: Adding the oak leaves to your Aquarium

When the boiling water has cooled down to room temperature, you can add the water (with tannins) and the leaves into the aquarium. The leaves should sink to the bottom almost immediately.

Pro-Tip: In case not all leaves have sunk, you either cramped too many leaves into the cup or didn't soak them long enough.

Boiled oak leaves sinking to the ground Boiled oak leaves sinking to the ground

Not boiling leaves

In case you didn't boil the leaves, they will float at the top of the surface for a long time until finally sinking to the ground. In case you added them without boiling and you don't want to wait any longer, you can still take out the leaves and boil them following the above steps.

Dried leaves which have not been boiled and float on the surface few days after being added to the tank Dried leaves which have not been boiled and float on the surface few days after being added to the tank