There’s a lot of confusion out there about the different kinds of live aquarium plants. Does this plant need to break the surface of the water? Shouldn’t all aquarium plants be completely covered by water? Even the terminology can be confusing—immersed, emersed, emerged, submerged, submersed.
What’s the difference between emersed and submerged aquarium plants? The main difference is that emersed plants grow partially out of the water, while submerged plants are completely underwater. There are several types of each plant for sale in local fish stores nowadays, and which is better is simply a matter of opinion and how you have your aquarium set up.
The type of aquarium plants you use in your tank could depend on the following:
- Your experience as a fishkeeper.
- Whether the plant will be fully submerged in your tank or not.
- How concerned you are about snails in your tank.
- What you’re willing to do to keep your plants alive.
I take a look at those factors and more in this article, including what you’ll need to do to make those emersed plants comfortable being fully submerged in an aquarium, so you can decide for yourself which best fits your needs.
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It’s All in the Meaning
There are several similar-sounding words that make plant type even more confusing than it needs to be. To clear things up, here are the most commonly confused/misunderstood words and what they mean:
Immersed: A plant grown completely below the tank’s waterline
Emersed: A plant that grows above the tank’s waterline (leaves, stems, flowers above the waterline)
Submersed: A plant grown completely below the tank’s waterline
Emerged: A plant with growth above the tank’s waterline (leaves/stems, flowers)
Submerged: A plant grown completely below the tank’s waterline.
As you can see, immersed, submersed, and submerged all mean the same thing, while emersed and emerged refer to the same thing. “Partially submerged” can also be used interchangeably with emersed or emerged.
For this article, I’m going to use emersed and submerged to keep things as simple as possible.
Sometimes these terms can be used to refer to how the plant was grown before it made it to your local fish store or your aquarium, and not to where it should be placed/how it should be grown in your tank.
I’ll explore this in more detail below.
Pros and Cons of Buying an Emersed vs Submerged Plant
Why would you choose one type of aquarium plant over the other? Does it matter? There are some pros and cons to both.
Typically, whether you shop at your local fish store, or buy your live aquarium plants online, you’ll have the option to buy plants that are already completely underwater (submerged) or partially above the water (emersed).
Emersed plants can be one of two things at your local fish store:
- Plants shooting above the waterline in the display tanks, like bamboo.
- “Dry” plants that come in plastic tubes, bins, or bags with a growth medium of some kind, like gel pellets, to keep the roots and lower parts of the plant moist.
Pros of Emersed Aquarium Plants:
- No water mess—if buying online, you don’t have to worry about the container leaking water and the plant dying before you even get it. If buying the plant in person, you don’t have to worry about possibly getting water in your car on the way home.
- These plants normally come with a “snail free”
- They travel well, meaning they hold up well during shipping, either to the fish store or your home.
Cons of Emersed Aquarium Plants:
- You have to take some additional steps to ensure the plant does well if it’s going to be completely submerged in your tank at home. I devote an entire section on how to convert an emersed plant to a submerged one in the next section.
- Limited selection—many local fish stores only carry a select variety of emersed plants.
To buy a submerged plant in person, a store employee would get a bag, fill it with water, take a submerged plant from the display tank, and place it in the bag. It’s the same process they’d used to select your fish from the tank for you to take home.
Pros of Submerged Aquariums Plants:
- You don’t need to do anything special to prepare the plant to be submerged in your tank since it’s already been growing completely underwater.
- Tons of plant options, from small to large, low light to bright light, red, green, or variegated, and even carpet-type plants.
- Fairly easy maintenance, depending on the type of plant.
Cons of Submerged Aquariums Plants:
- There’s always the risk of bringing unwanted snails home with you. Unfortunately, it doesn’t take much for snails to take over your tank, so always inspect submerged plants (and the tank they’re in!) very carefully for snails before selecting one to bring home.
- Water, water everywhere—just like when you bring home fish, you’ll need to be careful not to mix the water in the plant’s bag with the water in your tank. And spills can happen in the car on the way home or in your house before getting the plant into the tank.
- If the plant is being shipped to you, there’s a chance that the container holding the water that the plant’s being shipped in could leak before arriving at your home, resulting in dead or badly damaged plants.
You may be thinking that emersed plants are the way to go—I mean, no snails is a huge plus—and there are enough options that unless you have a certain plant in mind already, you should be able to find something that works for your tank.
But before you just throw your new plant into the fish tank, there are a couple of extra steps you need to take to be sure an emersed plant that’s going to be fully submerged in a fish tank doesn’t die on you!
How Do You Convert Emersed Plants to Submerged Plants?
Normally, if you own an aquarium, you’re looking for plants that keep most (if not all) of their growth underneath or just at the waterline, and aren’t looking for plants that will be growing above the waterline.
But emersed plants have been grown mostly above the waterline their entire lives, and may suffer if they’re put into a fish tank without taking a few precautions.
So, what can you do to ensure they’ll grow well when you submerge them in your tank?
- Add some CO2 to the tank to make the plant(s) happy. This is because plants grown above water have easy access to CO2 that they won’t have when switching over to being completely underwater.
Most of the time, fish produce enough CO2 for your plants to live on happily, but emersed plants are spoiled by having so much of the plant above water and taking CO2 directly from the air.
You can add carbon dioxide through several different methods, though some are fairly costly or unreliable. The most common ways to add CO2 are: by using a pressurized system (the most expensive), adding CO2 tablets to the tank (for small tanks only), pouring CO2 liquid formulas into the tank’s water, or electronically generating carbon dioxide.
One caution here: adding too much CO2 can be harmful or deadly to your fish—so this is probably not something for the beginning fishkeeper!
- Use fertilizer. Yes, you can buy fertilizer for aquarium plants! This should help with the transition from nutrient-rich soil or growth mediums to aquarium gravel/substrate.
You will need to understand your water parameters and water hardness to find the best fit for your tank.
Keep a close eye on the plants you’re transitioning to see if you need to make any adjustments.
Emersed plants are those that are grown above the waterline, with typically only the roots and lower parts of the plant under water. These are typically found at local fish stores in plastic tubes, cups, or bags with a growth medium covering the roots.
Submerged plants have been grown completely below the waterline and are typically sold in tanks of water at local fish stores.
Which type of plant you choose to add to your aquarium depends on:
- Your experience level.
- Whether or not the plant will be fully submerged in your tank.
- How concerned you are about snails.
- What you’re willing to do to keep your plants alive.
Emersed plants in a local fish store may be in better condition than submerged plants, and certainly a “no snail” guarantee makes them seem pretty enticing—but if you want to turn that emersed plant into a fully submerged plant, it will require some work. You’ll need to add some extra CO2 to your tank, and may want to include fertilizers, too, just to be on the safe side.