Sea Lettuce: What Eats Sea Lettuce in a Reef Tank?

It is not hard to see where sea lettuce gets its name, as its sheet-like, green and ruffled leaves bear a strong resemblance to the lettuce you keep in your fridge, but what should you do if it starts appearing in your saltwater reef tank?

While sea lettuce is harmless, it spreads quickly and before you know it, all the work and money you have put into your tank could be covered up by sea lettuce – algae. 

A smart way to keep its spread at bay is to incorporate organisms in your tank that are known to eat sea lettuce, as they will keep the sea lettuce nicely trimmed and controlled while benefiting from its many nutrients.  

What Is Sea Lettuce?

Not familiar with sea lettuce? Don’t worry, you might know it by its other name: Seaweed. Sea lettuce belongs to the genus Ulva and the family Ulvaceae, and it is a type of seaweed you can find in many saltwater reef tanks. 

In some cases, the tank owner may keep it there intentionally, and other times it could have just appeared. The good news is that sea lettuce is full of nutrients and highly edible for a number of other species, but the bad news is that it spreads easily and could start taking over your tank.

Sea algae are known for causing certain health concerns in the wild, and especially as washed-up algae decompose, but it is not the same as keeping it in your reef tank. In fact, sea lettuce (certain species) is consumed by humans in some parts of the world. It is known to be very rich in vitamin A, B, C, and iodine.

In the aquarium world, you can grow sea lettuce and even purchase dried sea lettuce as a nutritious additive to your tank. If you want to grow sea lettuce, it is surprisingly easy thanks to its adaptability. Changes in temperature and water conditions are unlikely to bother it, provided the sea lettuce gets enough light.


Let’s start by having a quick look at two of the main benefits that come with having sea lettuce growing in your tank.

With this in mind, you don’t need to worry about having sea lettuce in your tank, and you can instead focus on making sure it doesn’t take over. It is not harmful but doesn’t look great covering everything in a tank.

Another benefit is that it offers shelter to copepods and amphipods! The plant is shaped in a way that offers much-needed protection from predators.

Where Does Sea Lettuce Grow?

The most common place to find sea lettuce growing is on rocks in your tanks, on shells, or floating in the water. However, it can also grow on any other surface below or above the water, depending on what your tank setup looks like.

In the wild, different species of sea lettuce can be found growing worldwide, usually on rocks and rock-covered shores. If the sea lettuce detaches from a rock or other object, it can still continue living unattached and free-floating.

Certain species of sea lettuce can also grow in brackish waters. It grows all year round and not during specific times of the year, and sea lettuce lives for approximately 3 months. Some species grow more during the summer months, and it doesn’t grow in deep waters as it requires light to thrive.

What is interesting about the sea lettuce is that it adapts very easily to new environments and difficult surfaces, which is why it is able to live in conditions and on surfaces where most other organisms would be unable to thrive (or survive).

Organisms That Eat Sea Lettuce

Sea lettuce is a very underestimated tank component, as it can feed other organisms like tangs and keep the waters free from nitrate and phosphate. Many inexperienced tank owners discover the presence of sea lettuce and automatically think it needs to be removed, but this isn’t necessarily the case.

To get as much out of your sea lettuce as possible, you want your tank to have organisms that can feed off it, as it will keep it from taking over the tank and simultaneously provide said organisms with excellent nutrition.

What eats sea lettuce in a reef tank?

There are many different sea animals that eat sea lettuce, and these are the ones you want to make sure you have in your tank. Almost anything herbivorous is likely to take at least a bite or two out of the sea lettuce in your reef tank, but we have listed a few examples:

Having organisms that eat sea lettuce and benefit from its nutrients creates a healthy balance in your seawater reef tank, while also making sure the tank isn’t covered in somewhat unattractive, green seaweed.

Still Too Much Sea Lettuce – Now What?

Some tank owners continue to struggle with sea lettuce, and report that it appears to grow and spread faster than certain species can eat it. If this is the case, it is possible that something isn’t quite right.

One explanation could be that you don’t have enough sea lettuce-eating organisms in your tank, or perhaps that you don’t have the right ones.

When going through forum threads it is quite common to see incorrect advice, such as to add yellow cucumbers to combat the sea lettuce problem, but the issue here is that yellow cucumbers do not eat sea lettuce and are therefore rather useless in this aspect.

In some scenarios, you may have to remove some of the sea lettuce manually to help control its spread, but once you bring the right herbivorous organisms into your tank, the problem should solve itself.


Sea lettuce is a plant that is resistant to drastic changes in water temperatures and overall conditions, and this can cause it to spread fast. It can be found growing on rocks and surfaces in your tank, as well as float on the surface of the water.

Sea lettuce is not bad for your aquarium, but it may look unattractive if allowed to take over too much. The solution is to add herbivores, such as sea hares, sea urchins, and emerald crabs to the tank, as these will feed off the plant and keep it under control.

Most species of sea lettuce are packed with nutrients like iodine and vitamin A, B, and C, and it keeps the tank healthy by absorbing nitrate, phosphate, and more.