Hemianthus Micranthemoides Care Guide

Alison Page

Alison Page


Hemianthus micranthemoides

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Most hobbyists, myself included, love to include plenty of vibrant, living plants in their tanks. If you want a versatile, bright green plant that’s easy to grow in a tropical freshwater tank, Hemianthus Micranthemoides might be a species worth considering.

Read this guide to learn everything you need to know about growing and propagating this beautiful, beginner-friendly plant in your aquarium.

Hemianthus Micranthemoides – Overview

Heminathus Micranthemoides Info
Scientific NameHemianthus Micranthemoides
Common NamePearl Weed, Tank Pearl Grass
OriginNorth America
Ease of GrowingBeginner-friendly, easy
AquascapeCarpet, foreground, or floating
Height2 to 5 inches
pH6.5 to 7.5
Temperature66 to 82°F
Growth RateModerate to Fast
PropagationFrom stem cuttings
Light RequirementMedium
CO2CO2 is not required but can increase the plant's growth rate

What Is Hemianthus Micranthemoides?

Hemianthus micranthemoides, also referred to as Pearl weed, is an easy-to-grow aquarium plant that is loved for its bright green color and versatile growing habits.

You can grow Pearl weed in many parts of your fish tank and a range of conditions, including the foreground, as a dense, bushy carpet plant, fixed to pieces of rock or driftwood, and as a free-floating specimen.

Pearl weed comes from Florida, where it grows wild in wet areas, often in slow-moving or stagnant water.

Mistaken Identity

Pearl weed belongs to the Scrophulariaceae family and the genus Hemianthus. The plant is sometimes mistaken for Hemianthus callitrichoides, and fish stores often confuse the two, so be careful to buy the correct species when you go shopping!

The key difference between the two species is that Hemianthus callitrichoides plants typically have much smaller leaves than Hemianthus micranthemoides.

Is Pearl Weed Easy to Grow?

Pearl weed is extremely easy to grow under a variety of conditions, including in coldwater tanks, and no high-tech setup is required. That said, if you provide CO2 injections and optimize light and pH conditions, you’ll encourage healthy growth in this attractive plant.

How to Grow Pearl Weed as a Carpet

You can use Pearl weed to create a wonderful carpet across the bottom of your tank by planting it in the substrate to root and then regularly trimming and pruning the plant.

The propagation process is easy, and you can do that by snipping off pieces from a mature Pearl weed stem and planting them in the substrate, which will encourage the plant to grow and spread more quickly.

Can Pearl Weed Grow Floating?

One of the beauties of Pearl weed is its versatility. In addition to growing the plant in the substrate to create a carpet, you can grow it free-floating to create valuable shade and shelter for shy fish species and fish fry.

Can I Grow Pearl Weed On Decorations?

My favorite way to grow Pearl weed is on decorative rocks and pieces of wood by using a piece of fishing line or thread to carefully tie the plant to your chosen decoration.

The plant’s stems put out a well-developed root system that extracts nutrition from the water column, enabling the plant to quickly become established and flourish.

Can Pearl Weed Grow Emersed?

Hemianthus micranthemoides
Image via YouTube

In addition, Hemianthus micranthemoides can be grown emersed, as it does in its natural habitat in Florida.

However, you should know that the plant can “melt” if you move it from an emersed to a submersed environment and might start shedding its leaves until it settles in its new environment.

How to Propagate Pearl Weed

Like most stem plants, you can propagate Pearl weed under normal conditions by simply trimming off healthy stems and planting them in the substrate. If using pot or tissue plants, use a pair of aquascaping tweezers to plant the tiny plantlets.

You can prevent the tiny plants from floating away by using a few small stones placed around the stem’s base.


Since Pearl weed is a pretty common aquatic plant, you can buy it in most good aquarium supplies stores and from online retailers.

Hemianthus micranthemoides is relatively cheap to buy when you consider that it’s so easy to propagate, costing around $10 to $20 per plant, depending on the size of the specimen and where you purchase it.

You can buy Pearl weed as tissue culture or in pots. The tissue culture variant is lab-grown, so it’s safer and won’t contain algae and pest snails that could invade your aquarium.

Take care to buy healthy specimens of Pearl weed that have a bright green appearance and no visible damage.

Hemianthus Micranthemoides Care Guide

Tank Size

You can grow Pearl weed in tanks of various sizes, from 5 gallons upwards. However, note that if you grow the plant in a small tank, you’ll need to trim it regularly to control its growth and spread. For that reason, I recommend that you only grow this plant in a 10-gallon tank or larger.

Water Parameters

Pearl weed tolerates a wide range of water conditions. However, optimal water parameters are as follows:

  • Temperature from 66 to 82°F
  • pH 6.5 to 7.5
  • Water hardness 1 to 15 dKH and 1 – 20 dGH


Choosing the correct lighting is crucial to successfully growing any species of aquarium plant. Hemianthus micranthemoides need moderate light to grow. However, if you’re growing this as a tank carpet plant, you’ll need to provide it with high-intensity light.

Brighter levels of light will stimulate bushy, compact growth with plenty of runners, whereas a low-light environment typically results in more upward growth, greater spaces between the leaves, and darker coloration.

I recommend providing your Pearl weed plant with up to 10 hours of light daily for optimal growth and bright color.


You can grow Pearl weed in any kind of substrate, including gravel, sand, and aquarium soil, and the plant doesn’t need added nutrients to thrive.

CO2 and Fertilizer

You don’t necessarily need to feed the plant with fertilizer or give it additional CO2 to encourage growth, and the plant grows fairly well in low-tech tanks. However, the plant’s growth tends to be less dense and bushy without additional support.

Pearl weed is mainly a column feeder. Since its root system is quite weak, the plant takes up the nutrients it needs mostly through its leaves. For that reason, if you choose to feed the plant, I advise using liquid fertilizer rather than root tabs.

General Maintenance

Pearl weed is an adaptable plant that’s relatively easy to care for and maintain. However, you’ll need to trim the foliage occasionally to prevent the plant from taking over the entire tank!

The plant’s growth rate depends on what nutrients are available, whether you choose to use CO2 supplementation, and the intensity of the lighting in your setup. However, you’ll still need to keep an eye on the plant’s growth and spread and prune it when necessary.

If you trim Pearl weed regularly with curved pruning scissors, it will quickly grow quite bushy and start sending out side shoots to create an even denser plant.

If you decide to grow this species as a wonderful carpet plant, it’s important to know that it grows taller than other popular tank carpet plants, such as Baby Tears.

Growth Rate

Pearl weed is not a rapid-growing species until it takes hold. However, once the plant is established, it grows remarkably quickly, and you’ll probably need to trim it back weekly.

For that reason, when buying new Pearl weed plants to start a colony in a small tank, I recommend starting with one plant, which will rapidly cover the entire tank bottom in just a couple of months.

Your routine partial water changes and substrate vacuuming are essential for good plant growth and the health and well-being of your fish.

Tank Mates

Pearl weed is compatible with lots of different types of aquarium creatures, including the following:

  • Gouramis
  • Betta fish
  • Tetras
  • Platies
  • Mollies
  • Guppies
  • Rainbowfish

Basically, this plant is ideal for use in most community fish tanks. However, do be aware that if you’re growing a Pearl weed carpet appearance, bottom-dwelling species might not be the best choice.

All species of aquarium shrimp love Pearl weed, using the plant as an excellent place to hide and pick scraps of leftover food that drift down from above from the plant’s leaves.

Aquarium snails also make good tank mates for Pearl weed, although be sure to choose species that won’t damage the plants by grazing on them.

Tank Mates to Avoid

In addition to plant-eating snails, you should steer clear of fish species that like to eat or dig up plants, including Koi, goldfish, Jack Dempsey, Oscars, and African cichlids.

In addition, unless you keep Pearl weed as a floating plant, don’t have it in a tank containing freshwater crabs or crayfish, as these creatures will uproot, eat, and cut almost every type of plant you can keep in your tank.

Pearl Weed Troubleshooting

There are a few issues that aquarists experience when growing Pearl weed, and we discuss those, together with potential solutions, in this part of our guide.


Hemianthus micranthemoides

The term “melting” refers to the plant’s shedding of leaves. Melting is a phenomenon that generally happens when an emersed plant is transferred to a submersed environment.

Physically transferring Hemianthus micranthemoides triggers an adverse response that causes the plant to shed its leaves during the first few weeks in its new home.

But don’t panic! That’s a perfectly normal response by this and other stem plants. Once the plant is settled, it will happily grow in a submersed form and start putting out new shoots and leaves.

Yellow Bottom Leaves

When the Pearl weed plant becomes extremely dense, its lower leaves usually turn yellow and die back simply because they’re not getting enough light.

Regular trimming generally solves this problem since it removes the shade from the bottom leaves and also helps to maintain the plant’s overall bright green color.

Yellow Leaves All Over

If the plant leaves become yellow, that’s generally due to a lack of essential nutrients or if the pH levels in the tank are too high.

Final Thoughts

I hope you enjoyed our guide to growing Hemianthus micranthemoides or Pearl weed. If you did, please remember to hit the share button before you go!

Pearl weed is a beginner-friendly plant that you can grow in the substrate as a carpeting plant, fixed to your favorite aquarium decorations, or as a free-floating plant to provide shade and hiding places for your fish and shrimp.

Aside from regular trimming to prevent overgrowth, Pearl weed needs little maintenance. You don’t even need to feed it with fertilizer or provide CO2 supplementation to encourage good, healthy growth.

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