One of the popular plants for freshwater aquariums is water lettuce, a unique looking plant. However, many aquarists give mixed reviews of the plant. Some will tell you that the plant gives them no problems and looks beautiful in their tanks. Others have stories about how the water lettuce quickly got out of control and wrought more havoc than algae.
But what is it about water lettuce that makes people wary of it? Is water lettuce a good or bad addition to the aquarium? Let’s find out.
About Water Lettuce in Aquarium
Before we get into whether keeping water lettuce is good or bad, let’s first learn the basics. Here are some quick stats about the plant:
● Scientific Name: Pistia stratiotes
● Also known as: Nile cabbage or water cabbage; dwarf water lettuce is also available
● Care Level: Moderately Hard
● Lighting Requirements: Medium
● Maximum Size: 10 in (25.5 cm)
In your aquarium, water lettuce can look lovely—the network of roots forming a stunning maze for your fish and fry to dwell.
Water Lettuce Is Tropical
Originally, it was thought that water lettuce is from Africa, hence the name “Nile cabbage,” but that has been questioned. The plant was discovered along the Nile River, near Lake Victoria.
However, after that first sighting, water lettuce has been found all throughout the globe; whether this is caused by human handling or just natural progression and propagation, none can say.
However, because water lettuce can propagate so prolifically, it can be a danger to some ecosystems and threaten native plants and fish.
There are some places where transporting or growing water lettuce is illegal. For example, in Florida, you are not allowed to own water lettuce at all.
If you plan on adding water lettuce to your aquarium, be sure to check the local and state regulations.
Is Water Lettuce Toxic?
While water lettuce can be found throughout the world, it is often considered toxic because of a penchant for clogging irrigation. It can block the air-water interface, limiting gas exchange.
Mosquitoes may also breed in the stagnant water that collects in the leaves.
The greatest danger, however, may be to small children and pets. The leaves of water lettuce contain a poisonous compound called calcium oxalate. The chemical can burn the mouth and even cause kidney damage.
If you have small animals and children who like putting things in their mouth, then you should not use water lettuce.
Water Lettuce Cannot Survive The Cold
As noted above, water lettuce was originally found in a tropical climate. This means that, while it can grow in more temperate regions, it cannot tolerate cold temperatures. Water lettuce thrives in warmer water, so you will have to ensure the aquarium does not dip lower than 60 degrees Fahrenheit. Otherwise, you will kill off your aquatic plant.
Water Lettuce Doesn’t Require Soil
As your water lettuce starts to grow, you will notice the long tendrils hanging down from the floating portion. Depending on the find of water lettuce you have—regular or dwarf—the roots might stay around 2 inches long. Other times, you might have 10 inches of root dangling around the substrate.
However, this doesn’t mean that the water lettuce is trying to get to soil. These plants are fully capable of growing and thriving without ever needing to touch soil. They will get enough sustenance from the water and sunlight alone.
Water Lettuce Has Uniquely Shaped Leaves
One of the reasons aquarists love adding water lettuce to their tanks is how ornamental it looks. The plant has a very peculiar aesthetic, and the bright yellowish green of the leaves is visually stunning. As for the leaves, you will notice it has a rosette pattern.
When you touch the leaves, you might find them softer than anticipated. There are fine hairs on the leaves that are meant to cling to water and allow for greater surface area, promoting buoyancy.
The leaves tend to get thicker and more like lettuce towards the center of the plant. Eventually, as the water lettuce grows and propagates, it can form a thick mat.
Propagating Water Lettuce
Here is something interesting about water lettuce: It can reproduce both sexually and asexually. However, sexual reproduction is rather difficult in a home aquarium or even a small pond.
If you are curious though, then you can take a peek at the center of a matured water lettuce plant. You might see that there are tiny buds or flowers at the center. All water lettuces have these flowers, but some are male and others are female. If fertilization is successful—through the exchange of pollen—seeded berries form.
Asexual reproduction is much more common, because it is easier. You will notice that some plants have “daughters,” or a smaller version that floats alongside the mother plant. They are connected by a thin stolon.
During this reproduction process, the water lettuce might form a dense “mat” that covers the surface of the water. Don’t let your plants cover the surface of an aquarium. Ever. This will prevent light from penetrating the depths and may suffocate your fish.
That said, if you purchase water lettuce and notice that it looks rather weak, remove the yellowed and decaying leaves, as well as old daughters. This will ensure rapid propagation.
From there, all you need to do is maintain the rate of growth and keep the mat from going out of control.
Be Careful of Other Aquatic Plants
If you plan on adding water lettuce to a tank with established plants, be careful. There is a reason why local and state governments have regulation against water lettuce.
Once water lettuce starts to grow, it has a tendency to choke off other plants, killing the competition. Think of it as weeds around a rose bush in that case.
For plants in the substrate, the mat made by water lettuce will reduce the overall amount of light they receive—and they could die. Also, the roots of water lettuce will cut down on oxygen and can mess up pH balance.
Some places with dense water lettuce growths are also overrun with mosquitoes that carry malaria (particularly in Africa), so be careful. And again, make sure water lettuce is allowed in your area.
What Are Some Additional Uses of Water Lettuce in Aquarium?
Now, let’s consider some of the reasons why you should have water lettuce in your aquarium. What are the benefits? One of the best reasons for adding live plants to any aquarium is the overall appeal. Water lettuce, once established, is hardy and beautiful.
Other reasons include:
Fish Can Eat It
Water lettuce is a good addition to tanks. Most fish will enjoy having it around, but cichlids are more likely to destroy it. Goldfish and other herbivorous fish will tend to eat the roots along the leaves, so it isn’t a good plant for goldfish as well. Keep that in mind if you plan to get water lettuce.
That said, the leaves and roots have not been identified as toxic to fish.
Low Chance of Algal Bloom
Another reason you might choose water lettuce is for the reduction in algae. While water lettuce can become problematic if you don’t maintain it correctly, algal blooms are far worse.
Although the reason is unknown, water lettuce seems to prevent algae growth. Water lettuce can absorb minerals and other elements in the water, like low quantities of mercury, to keep the water in the tank from becoming toxic to the fish and other plants.
Caring For Water Lettuce In Aquarium
Keeping water lettuce in the aquarium can be difficult at times. As mentioned before, the plant can reproduce too quickly. You will need to keep a careful watch on the mats and trim the roots and growths to prevent it from getting out of control.
Also, when you throw the water lettuce clippings away, make sure you aren’t just throwing them outside, as this could cause infestation in the long run.
Requires Little Light
Like most plants, water lettuce likes having sunlight—but not too much. Cultivated water lettuce for aquariums needs to be introduced to sunlight gradually. Otherwise, it will shrivel and die.
An artificial light source mixed with some shade is perfect for growing water lettuce. T5 or T8 bulbs are ideal in the beginning. Avoid placing new water lettuce directly in sunlight for the first few weeks.
Watch The Humidity
Another reason water lettuce can be a challenge is that the plant is finicky about humidity. Water lettuce needs a lot of moisture to grow. For aquarists who live in less humid regions, you should consider covering the tank. That way, your water lettuce will get enough humidity and grow quickly. Once the plant has grown a little, you won’t need to use the lid as often.
A lot of aquarists will tell you that growing water lettuce in a tank with a strong current is next to impossible, that they aren’t wrong. If you have a hang-on back filter, you may have some difficulties getting your water lettuce to grow.
Sometimes, the current will push the plant around the tank, and they can be submerged and damaged if they get into the filter’s outflow.
If you decide to use water lettuce in your fish tank, then you are going to have to put it in a contained area. Some fishkeepers do this by “roping off” a corner with clear tubing.
That way, you can let it grow until it forms a mat on the surface of the water without it getting swept up by the current. Once the lettuce grows enough, it will be more stationary.
What About Dwarf Water Lettuce?
Dwarf water lettuce is a slightly different variant. While some will argue that dwarf water lettuce is the same as regular water lettuce, the evidence has not been conclusive.
The belief is that water lettuce becomes dwarfed when the seed pods are introduced to a less nutrient rich environment than the mother. This results in a stunted version of the more ubiquitous kind of water lettuce.
If you decide to get dwarf water lettuce in place of water lettuce, you may notice that it is much easier to take care of. The roots also do not grow as long.
Also, they do not grow out of control and form mats as quickly as regular water lettuce. That said, when left unchecked, dwarf water lettuce can get big—over 10 inches in diameter!
Which Is Better: Dwarf Water Lettuce or Frogbit?
Now, a lot of aquarium enthusiasts ponder this question: Is water lettuce better than frogbit? Or is frogbit better? Because both plants look similar to one another, it is easy to get confused and wonder if there is any difference.
The only true difference is that frogbit has leaves that will stand up and thicken, widening outward rather than looking like cabbage.
Frogbit can also get bigger than water lettuce, sometimes growing as big as 20 inches in diameter. Frogbit also requires water between 64-84 degrees F and a pH between 6.0-7.5.
Therefore, while frogbit might be an adequate substitute, it can be just as difficult to care for and maintain as water lettuce.
Frogbit is also not toxic, so it might be a wiser choice for houses with small children and animals.
Verdict: Is Water Lettuce in Aquarium Good or Bad?
There is a lot to be said about water lettuce. On one hand, it is a vivid and bright addition to any aquarium.
It can be a wonderful ornament and will help with cleaning the water when kept under control. Fish and smaller fry love the roots that dangle down. Conversely, water lettuce is often seen as a pestilence for natural environments and can be toxic to small children and animals.
Also, if it gets out of control in a tank, it can ruin the gas exchange and lower the oxygen in the water.
If you never have tried working with aquatic plants before, do not choose water lettuce as your first plant. There are plenty of others that are easier to care for.
That said, if you have experience and would like to grow some water lettuce (and you live somewhere that doesn’t have regulations against it), then the challenge might be right for you.