|Common name(s)||Water cabbage, Nile cabbage, shell flower, water bonnet|
|Scientific name||Pistia stratiotes|
|Growth rate||Water lettuce leaf population doubles in three weeks or less|
|Placement in aquarium||Floating|
|Color||Light green, Grey-green|
Water lettuce (Pistia Stratiotes) is a floating freshwater plant that grows mainly in streams, ponds, and lakes. The plant has broad fuzzy parallel-veined leaves similar to those of lettuce. That is why water lettuce is also called water cabbage. You can also grow it in an aquarium to cover the aquarium water surface against sunlight and algae infestation.
Water lettuce thrives at a pH of 6.5 – 7.5 and medium to partial light. You can use a full spectrum artificial fluorescent light number T5 or T8 for your aquarium to provide light. The ideal water temperature for growing your water lettuce is between 72-86°F (22-27°C).
Water lettuce keeps algae under control and cleanses toxic metals present in water, including ammonia and nitrates. If you don’t have algae-eating fish like guppies, this plant is a great solution to the control of algae in your pond or aquarium.
Water Lettuce profile overview
Water lettuce originated from South Africa and was first spotted in the River Nile in the early 1800s. The plant has spread over the years and can now be found on all continents except Antarctica.
How to grow water lettuce in your aquarium
You can grow water lettuce from seeds or by propagation. The plant has long, hairy roots and grows well in an aquarium. It is the lightest floating plant you can grow as an alternative to the duckweed. If you don’t position it correctly in your aquarium, water lettuce can proliferate and stress or even kill your fish.
Here is a guide on how to grow water lettuce safely in your aquarium through propagation:
- Cut and separate young water lettuce from the parent plant
- Place the new water lettuce in a separate tank (not your aquarium) under moderate lighting conditions.
- Leave the plant in a separate container for four weeks as you change the water until the water has the same water quality as your aquarium.
- After four weeks, remove the plant and transfer it to your aquarium.
- Place the water lettuce to float at the top of the tank. Ensure the water parameters are the same.
- Observe the plant for four weeks and note any changes. Due to stress and new environmental conditions, the plant may shed its roots in the first week. There is no need to raise the alarm if that happens. The plant will grow new roots after 3-4 weeks.
Tip: The minimum tank size for keeping your aquarium fish and water lettuce should be 10 gallons.
Water Lettuce care
Water lettuce grows fast and takes up a lot of aquarium space. The plant requires elaborate care and maintenance to keep it from spreading and suffocating your fish.
Here are some ways to care for water lettuce:
Remove the daughter plant from the mother plant
As water lettuce grows more prominent, it develops fresh roots and leaves from the sides. These are called the daughter plants. Remove the daughter plant from the main water lettuce to prevent the plant from spreading rapidly throughout your aquarium.
You can propagate the pruned plant parts if you need more water lettuce in your aquarium. Otherwise, remove them every week and dispose of them.
Remove the central stalk and let the new water lettuce thrive
The second way of maintaining the size of the plant is by removing the mother plant and letting the daughter plant grow. Allowing the young plant to grow will slow down the plant growth and eliminates potential diseases with the old water lettuce.
Other than pruning or propagating, water lettuce doesn’t require nutrient addition. It gets enough nutrients from the water for healthy growth.
Hard water can discolorize water lettuce leaves and turn them pale, making the plant less attractive. Remember, water lettuce is a freshwater plant. However, water lettuce tolerates a range of water conditions in an aquarium. It will thrive in soft to slightly hard water.
Aquarium water pH
It is best to grow water lettuce in a slightly acidic to neutral pH range of 6.5 – 7.5. The plant does not tolerate more than 2.5 parts per thousand salt in water.
Water lettuce is a low-light aquarium plant. It requires low to medium light to grow healthy. Place your aquarium near a window for natural sunlight to reach out to it. However, too much sunlight can yellow the leaves and damage the plant. If your house cannot provide a suitable place, use a full spectrum artificial fluorescent light number T5 or T8.
The best place to grow the plant is in the aquarium at any one corner of the tank. While it is not a a midground aquarium plant, you can use it as a floating plant to provide plenty of cover and hiding spaces for your fish. You can also use strings to tie the plant roots gently to the substrates at the bottom of the tank. Tying the water lettuce prevents it from moving, especially if your aquarium registers significant water movements.
You can read more about anchoring aquarium plants here.
Water lettuce is a floating plant; thus, it does not require to be rooted in soil or sand to grow. It floats on top of the aquarium and reaches about 6 inches tall. Water lettuce is known for its rapid growth and scatter. The plant will often cover the tank and kill fish if placed incorrectly in the tank.
Water lettuce gets all its nutrients directly from water, and adding other nutrition supplements is not necessary. The plant absorbs nutrients using its long roots and stores them adequately.
That means it can grow in your aquarium without substrates. Add substrates such as stones or tree branches only for your aquarium livestock and the beauty of your tank.
You can grow water lettuce either indoors or outdoors. Regardless of where you decide to grow it, ensure the water temperature for the water lettuce is around 72-86°F (22-27°C). That temperature is best for the plant and the pets inside your aquarium.
Fertilizer and CO2
If you notice your water lettuce leaves turning from green to yellow or pale, there may be a lack of nutrients in the water. If the aquarium has fewer nutrients, you will need to supplement the plant with safe fertilizers; excess fertilizer may harm the plants and the fish.
The best way is to remove the plant and fertilize it separately. Remove the water lettuce from the aquarium and place it in a container with liquid fertilizer. Allow the plant to absorb the nutrients for about 5 hours and put it back inside the tank.
Most importantly, ensure that the CO2 concentration in the aquarium is less than 1200 ppm.
Common problems of water lettuce in aquariums
Growing water lettuce and watching them spreading and supporting the aquarium livestock is a satisfying experience. However, most people tend to pay more attention to the fish than the plant, leaving the water lettuce to wilt and die.
Here are some common problems water lettuce may face while growing in an aquarium:
1. Leaves turning yellow
Healthy water lettuce leaves are light green. If you see the leaves turning from green to any other unsightly color, there is an imbalance in your tank water parameters. The problem may be inadequate lighting or insufficient nutrients.
Fix discoloring water lettuce leaves by correcting the tank water conditions or providing the water lettuce with adequate lighting necessary for photosynthesis. Use artificial light or place the aquarium near a window that allows partial sunlight.
2. Rapid water lettuce growth rate
The rapid growth rate of water lettuce is the most common problem experienced by aquarists. Water lettuce grows to double its population in three weeks. It might require weekly prunings or propagation if you have large or multiple aquariums. That is usually so tedious.
Remove either the mother or daughter plant to curb the rapid growth rate of water lettuce in your aquarium.
3. Patches on the leaves
When your water lettuce starts developing patches on the leaves, it means your aquarium has a problem. The suitable water type for water lettuce is soft to slightly hard water.
But if the water is moderate or extremely hard, it forms a foam at the upper layer of the aquarium that affects the leaves. Save the water lettuce by changing 30% of the hard water with fresh water every week or two, depending on your tank size and fish type.
Benefits of water lettuce for aquariums
Despite having a fast growth rate and weekly pruning, water lettuce also has excellent benefits.
Here are some benefits of water lettuce for aquariums:
1. Algae control
Water lettuce grows fast and forms a blanket layer at the top of the tank. This layer blocks light from reaching the bottom of the tank, thereby controlling the algae population in the aquarium. Additionally, the plant absorbs more nutrients from the water, leaving very little for the algae to thrive.
2. Aquarium livestock protection
Water lettuce has long roots that provide adequate shelter and protection to your aquarium livestock. The plant is also essential for breeding fish. It provides fish fry with more playing and hiding places away from aggressive tankmates.
3. Toxins absorption
Water lettuce helps clean and cleanse the aquarium water. The plant absorbs by-products such as CO2, ammonia, nitrates, and nitrites excreted by the fish into the water.
Water lettuce also plays a significant role in removing heavy metals from the water. It then releases oxygen as the by-product, improving oxygen circulation in the water.
4. Water lettuce is easy to propagate
It’s easy to grow more water lettuce in water simply by propagation. As the plant grows, the new leaves at the bottom can be chopped off carefully and grown into new plants.
If you want more water lettuce in different tanks, simply propagate the plant instead of buying another water lettuce.
Water lettuce has a broad rosette leave that is attractive from the top. When you view them from the sides, the leaves offer an aesthetic and breathtaking look. Moreso, if you clean the tank and care for the water lettuce regularly.
Varieties of water lettuce
The plant comes in three different varieties.
- Pistia stratiotes Splash: It’s the rarest variety of water lettuce. Unlike the other varieties, splash lettuce does not grow so big.
- Pistia stratiotes Ruffles: As the name suggests, this water lettuce has ruffled leaves. It does not grow so huge and is suitable for aquariums.
- Pistia stratiotes Jurassic: Its variety produces large rosettes that can grow up to 12 inches wide. Despite its wide rosettes, Jurassic lettuce grows slower than the rest.
- The University of Florida. (2022). Pistia stratiotes. Center For Aquatic and Invasive Plants.
- Mid West Invasive Species Network. (nd.) Water lettuce (Pistia stratiotes)