Dwarf water lettuce, scientific name Pistia stratioes, is a member of the arum family of floating aquatic plants that you’ll see in many garden ponds and aquariums.
The water lettuce is not only beautiful, but it can make a very beneficial addition to your tank. The plant propagates very rapidly, providing shady areas in the aquascape that will improve the survival rate of baby shrimp and fish fry. Although it’s a pretty tough customer, the dwarf water lettuce does require the right water conditions and correct care for it to thrive.
In this guide, we explain how you can cultivate and enjoy this attractive floating plant in your display tank.
What is dwarf water lettuce?
The water lettuce is also known as Nile cabbage and water cabbage.
Pistia stratioes are floating plants that live and grow on the surface of the water. The plants are believed to be native of Africa, where it was first found near Lake Victoria on the Nile River. Documented research by the famous botanists of Ancient Greece suggests that the water lettuce was introduced some 2,000 years ago.
Since its rediscovery, the plant has spread to every continent in the world, with the exception of Antarctica, where temperatures are too cold for these frost-intolerant plants to grow.
Where the lettuce grows wild in bogs, lakes, and marshes, it presents a threat to native fish and vegetation. For that reason, it’s now illegal in some countries and states to transport or plant these floating plants. So, if you’re planning on introducing water lettuce to your aquarium, you should check with your local government agency first.
What does water lettuce look like?
These floating plants are cabbage-like in appearance with wavy-edged leaves that have attractive parallel veins decorating each leaf. The leaves are covered with short, soft hairs that trap air, assisting with the plant’s buoyancy.
The plant produces flowers that are hidden amidst the leaves, and the plants also bear rounded berries once fertilized. Underneath the plants, there are long blackish or white-colored roots that can extend for over a foot, providing refuge and spawning areas for fish.
The dwarf water lettuce can grow to measure up to 10 inches across, although the plants are usually much smaller when grown in a home aquarium setting, reaching just four inches in diameter.
How to care for dwarf water lettuce
Before you decide to introduce these floating plants to your aquarium, you should know that they can grow exponentially, given the right care and conditions. So, you must remove a few plants each week during routine tank maintenance.
Given the right conditions, dwarf lettuce grows very fast and can occupy a lot of space. For that reason, a 10-gallon tank is the smallest aquarium size that is needed for this plant species.
Dwarf water lettuce prefers slightly shady conditions and doesn’t do well in very bright light that may scorch the leaves. A regular setup using full-spectrum T8 or T5 small-sized bulbs should be sufficient to grow these plants. However, most of these floating plants are grown in shady conditions, so be sure to introduce brighter lighting conditions gradually, so avoid stunting the plants’ growth.
If the lighting in your aquarium is too bright, the plant’s leaves will turn yellow, brown, or reddish.
Water lettuce needs a humid environment of over 70 if it is to grow well. If the atmosphere in the room where you have your aquarium is dry, you might want to consider adding a lid to your tank if you don’t already have one.
Because it’s a floating plant, dwarf water lettuce doesn’t need CO2 supplementation. Also, fertilizer is not required unless your water is very low in nitrates, or you are very keen to cultivate the plants.
These plants can tolerate a wide range of water conditions. However, the ideal pH for the plants is soft to slightly hard, ranging from 6.0 to 7.5 pH.
The plants are tropical, thriving in warm water with a temperature ranging from 720 to 860 Fahrenheit. Note that the plants will only grow when the water temperature is above 640 to 680 Fahrenheit
These plants do not grow well in a tank that has a powerful filtration system that generates a strong current. So, if you want to keep the plants small, keep the water flow gentle, which will help to prevent overgrowth.
You can prevent the plants from being shoved around too much by the current by installing some form of barrier that keeps the plants away from more turbulent water. Try using a floating rube or rope to split the surface area and keep the plants in place.
Pistia is a surface plant that doesn’t need any substrate in which to grow.
Keeping dwarf water lettuce tidy
Pistia is a very rapid grower that needs to be managed if you don’t want the plant to overrun your aquarium. Take care not to allow the plants to completely cover the water surface by pinching off any plantlets or removing individual plants each week to keep a small gap between each one.
If the roots are allowed to reach the floor of the aquarium, they can get tangled in other plants or tank decorations. To keep root growth under control, remove the plants every two or three weeks and cut the roots, leaving about four inches of root remaining. Don’t worry; the plants will recover quickly and will come to no harm.
Note that, if the plants are dragged underneath the surface, they will quickly die off.
Where to buy dwarf water lettuce
If you fancy the idea of having some of these attractive plants in your aquarium, you can choose to either purchase an aquarium-ready plant or grow one yourself. If your local fish store doesn’t stock these plants, a quick search on Amazon will quickly find a few suppliers. Failing that, you could email local fish stores and pond supplies outlets to order a few plants.
Just as you would with a new fish, shrimp, or snail, you must quarantine your cabbages for a short time before adding them to your display setup.
Mail order plants from unfamiliar suppliers can carry parasites, snails, or predatory creatures, such as damselfly and dragonfly nymphs. Although you can add chemical treatments to the quarantine tank to kill off such undesirable creatures, shrimp, invertebrates, and some species of fish are highly sensitive to them and could be harmed when the plants are introduced to the habitat.
How to grow your own
Water lettuce can propagate sexually or asexually. However, sexual propagation is not particularly common in a home aquarium setting. The tiny flowers of this floating plant are found toward the middle of the lettuce and can be either male or female. When sexual fertilization is successful, you’ll see lots of tiny berries that contain seeds at the center.
Asexual propagation is commonly observed in an aquarium setting. During the process, the small daughter lettuce begins to float beside the mother plant, and they are joined together by means of a stolon. When asexual propagation takes place, thick mats of new lettuce are formed, quickly covering the surface of the tank.
Problems with water lettuce
There are a few noteworthy problems that can occur when growing floating plants.
Sometimes, new mail-order plants may shed some of their roots due to the stress of shipping. That’s not a cause for concern, as the roots will quickly grow back.
Shrinking or discolored leaves
If you place a cover on your tank, you may starve the plants of light, causing the leaves to become smaller.
Sometimes, the plants’ leaves will lose their green coloration, turning yellow, brown, or reddish. That’s usually caused by exposure to direct sunlight, especially bright lights, or long-term nutrient deficiency. Also, older growth is often yellow in color. In that case, simply peel off yellow leaves that are at the bottom of the plant.
If your plants are slow to grow, it’s likely that the water in the habitat is too cold, too hard, or there are insufficient nutrients in the water column.
Nile cabbages are prone to overgrowth, swamping your whole setup in a very short time and potentially destabilizing your aquarium’s natural ecosystem. The best action to take to control plant growth is to remove a few of the new plants each time you clean your tank.
Be aware that, if you allow the cabbages to cover every bit of the water surface, flora growing on the tank bottom will not receive sufficient light and may die. Also, surface feeding fish and labyrinth breathers, such as bettas, may struggle to live in an environment that contains these plants.
Sometimes, mosquitos set up shop amid the hairs on the plant’s leaves. Keep a check on the cleanliness of your setup and watch out for mosquito larvae in the water.
Why dwarf water lettuce is good for the aquarium
Pistia stratioes has many benefits for the aquarium.
Water cabbage competes directly with algae for nutrients, quickly removing the algae’s food source and preventing it from growing. While that may be great news for your tank’s overall appearance, low quantities of algae could spell disaster for algae eaters, such as shrimp and some fish species who may not get enough to eat. Be sure to supplement the diet of those animals affected by providing them with algae wafers.
Nile cabbage is extremely helpful for the hobbyist in that it can remove ammonia and nitrates from the water in double-quick time. Low levels of both these substances are great news for your aquarium community.
Also, the plants absorb spoiled food, organic waste, and heavy metals, helping to keep the environment healthy and clean.
As previously mentioned, the cabbage’s foliage and dangling root masses give full cover for shy fish species and shrimp who like a hiding place.
Also, the full surface provided by the cabbage leaves provides the best platform for the growth of beneficial bacteria.
Water lettuce with its long, feathery roots can make the perfect shelter for shrimp and small fish species. The surface-to-floor roots may offer protection for fry and smaller varieties of fish.
Although shrimp will not harm the plants, certain herbivorous fish may eat the edible roots. Also, larger species, including goldfish, can cause damage to the lettuce’s leaves.
There are many species of snails that will not cause any damage to the plants, including:
- Nerite snails
- Ramshorn snails
- Japanese trapdoor snails
- Malaysian trumpet snails
- Mystery snails
In addition, although creatures such as crabs and crayfish will readily uproot and eat plants that are growing in the substrate, they won’t touch floating vegetation, so water lettuce is the perfect choice for a habitat that includes these animals.
In this section of our guide, we answer a few of the questions asked by hobbyists who are wondering whether to add dwarf lettuce to their aquarium.
Q: Is water lettuce good for an aquarium?
A: Yes, there are several benefits of adding these plants to your setup. Shy fish, shrimp, and fry can take shelter among the trailing roots of the plants, beneficial bacteria may grow on the leaves’ flat surfaces, and the plants absorb harmful substances, including nitrates and heavy metals, from the water.
Q: Does water lettuce multiply?
A: Given the right conditions, the plant grows fast, multiplying by asexual and sexual reproduction.
Q: How quickly does water lettuce grow?
A: These plants grow well and fast, quickly increasing in size if given the correct care. In fact, you may need to remove a bit of the growth and any dead leaves each week.
Q: Is water lettuce toxic to fish?
A: Water lettuce leaves are full of toxic calcium oxalate crystals, which can be poisonous if eaten by animals and children. However, the plants are harmless to fish, unless they are allowed to cover the water in full, depleting oxygen that could kill your fish.
If you want a water plant for your aquarium or garden pond that grows in no time, gives full water surface coverage and grows best in shady sites, the name for which you should search on Amazon is the dwarf water lettuce.
Bear in mind that the plant is considered to be an invasive pest species right along the Eastern seaboard, throughout the southern U.S., and into California, Arizona, and Texas. So, if you live in any of these locations, you should seek an alternative.