Hemianthus Micranthemoides, An Excellent and Resilient Aquarium Decor

Published on September 13, 2019
Hemianthus Micranthemoides, An Excellent and Resilient Aquarium Decor

Hemianthus Micranthemoides or pearl grass is a household name in aquarium decor, but you probably didn’t know much about how they survive in there. For sure, you see these pearl weeds are those beautiful, fluffy squabs that make tanks look like the real deal.

However, we’re sure you still don’t know what made them one of the most recommended plants for tanks. Allow us to take you on a trip to its history down to its maintenance for a killer aquascape.

The Origin

pearl grassHemianthus (Micranthemum) Micranthemoides’ origin can be traced back to North America. Hemianthus micranthemoides thrives in the following habitats: freshwater, lacustrine (lakes), palustrine (marshes), riverine (rivers), and saline (tidal).

However, some sources say that aquarists these days do not anymore classify pearl weeds known as Hemianthus Micranthemoides. The indigenous Micranthemums are already extinct.

According to a few reports, the last time anyone has seen the native ranges of the Hemianthus Micranthemoides was in 1941. The last known location for these plants was in the Mid-Atlantic region of the United States.

In that case, the tank pearl grass we know is likely Hemianthus Glomeratus instead. However, this is based on a few differences between the native Micranthemoides and the pearl weeds used in aquariums.

No proper research has confirmed that tank pearl weeds aren’t H. Michranthemoides. H. Glomeratus plant species are absolute look-alikes of pearl grass though, so it makes sense why some sources made such assumptions.

How Hemianthus Micranthemoide Looks

pearl grass aquarium

Speaking of how Hemianthus Micranthemoides looks, let’s dive into its accurate description. Pearl grass has small, bright green arched leaves that make it look like a mini version of Egeria.

The pearl grass’s leaves also resemble teardrops a little bit, so many people usually confuse it for Baby Tears.  However, you can easily distinguish pearl weeds from other plants by checking their stem.

Pearl weeds have the shortest stems among other tank plants and Hemianthus species. So they are low-growers, hence a favorable beginner’s aquarium plant.

Guide on Growing Hemianthus Micranthemoides

Pearl weeds may be the least challenging tank plant to grow, but some aquarists still struggle in maintaining their cushiony look underwater. Hemianthus micranthemoides looks its best in the aquarium when it’s horizontal, but since its normal growth orientation is vertical, it is tricky.

To know more about how you can keep them branching out sideways, we’ve put together this mini manual for you.


Hemianthus Micranthemoides has a medium difficulty level. Sure enough, its short stems still require some work.

It’s the necessary regular trimming that makes it a little high maintenance. However, it’s worth all the effort as pearl grass grows fast.


As mentioned, it’s all about trimming on this one. Make sure you always cut the top part of the plant with curved scissors to prevent the bottom half from dying.

We also mean every day after the pearl grass has already settled for two weeks in your tank. It applies to whether you’re using pearl weeds as a carpet, foreground, or midground.


When planting plants like the Hemianthus Micranthemoides, the substrate used is a fine powder-type one. We recommend you use fine gravel. They do not tend to crush your pearl weed’s fragile stems and allows the roots to proliferate.


Like the aquatic pets in your tank, your Hemianthus micranthemoides also needs proper lighting. They need it for nourishment and better display purposes, of course.

Your pearl weed will flourish the most under a medium-bright light. However, many aquarists suggest the use of intense lighting as pearl grass is a low-lying plant.

A low amount of light won’t penetrate the water deep enough to reach the pearl weeds at the bottom. Bright lighting may affect your aquatic pets, though.

Medium strength lights are sufficient to get into the tank water depth. They also have enough brightness to induce fast growth.

Ideal lighting: 4-5 watts a gallon

Carbon Dioxide

You’re probably familiar with how Carbon dioxide or CO2 increases photosynthesis, which spurs plant growth. It might not have hit you until now, but if CO2 dissolves in water, how do pearl weeds grow in the aquarium then?

Here are a few types of aquarium CO2s that make plant growth possible in underwater:

Pressurized CO2

This CO2 comes in a pressurized bottle with an electronic solenoid valve. The solenoid valve allows the entry of the CO2 into the aquarium during the daytime.

The primary function of this CO2 is to prevent pH swings from happening at night as it is harmful to the fish.  This easy-setup works wonders, but it is the most expensive CO2 option whose refills are also hard to source.

CO2 Liquids

Also known as Seachem excel, CO2 liquids do not pump CO2 directly onto the plants. They are a liquid formula just poured into the water.

No pearl grass will benefit from this as this solution is only suitable for nano tanks with little CO2 consumption. Since the liquid doesn’t aim onto anything, it is cost-inefficient and frustrating to use in the long run.

The only good thing from this formula is the reliable and instant algae defense it provides.


It is the cheapest CO2 source in this list. All you need is to gather home ingredients and hardware materials to create one.

Keep in mind that DIY CO2 will produce a layer of slime in the standard diffuser. Injecting it straight into the tank filter will solve it and allow successful execution.

Electric CO2

We only recommend electric CO2 to small tank owners. Higher levels of CO2 in an automatic CO2 is quite expensive.

However, this is the most convenient option in this list, so it’s worth the bucks. An electrolyzed carbon insert produces carbon dioxide into the tank.

Refills for this option are tailored for specific machines, so they are still the last choice for average aquarists. They may be handy, but the costs will cause a great deal of inconvenience.

CO2 Tabs

These are the least known CO2 sources in the market. It has a visual dosage style that can only serve nano tanks.

No pearl grass can flourish with this long-term as these tabs get expensive over time even for small tanks which they are most suitable for. They are easy to use, but they have limited application, which dragged their reputation down over the years.

Water and Temperature

Just when you thought proper lighting and some CO2 were enough, here come the numbers you have to watch even more strictly. Pearl grass is sensitive to water and temperature conditions, and failing to maintain one aspect can kill your tank plant in an instant.

Here are the specific measurements you need to keep your pearl weeds healthy:

  • Recommended pH range for the species: 6.3 - 7.2
  • Recommended water hardness (dGH): 4 - 18°N (71.43 - 321.43ppm)
  • Recommended temperature: 19 - 27 °C (66.2 - 80.6°F)

The numbers show that the Hemianthus Micranthemoides need soft and acidic water to live.


When we said that pearl grass is all about the trim life, it certainly is even with breeding them. You have to cut them to multiply--that’s the principle.

These are the easy steps to propagate your pearl weeds:

  • Cut from any stems of the mother plant
  • Take the bottom leaves off
  • Place the cuttings into the substrate (make sure you don’t crush the stems so the roots will grow fast)
  • Some Hemianthus micranthemoides growers also place the cuttings horizontal to create mini vegetation in front of the tank

Aquascaping Tips

Hemianthus Micranthemoides is one of the most versatile tank plants despite being a stem species. Here are the ways pearl grass can make your aquarium look like the real under-the-sea.

  • Foreground plant: when trimmed short
  • Carpeting plant: requires careful cultivation
  • Midground plant: when left to grow bushy
  • Background: applies the best for nano aquariums; the small leaves of the pearl grass do the trick

Benefits of Having Pearl Grass in Your Tank

So you already know how to maintain pearl weeds, but what do they contribute to your tank? Sure, they make the aquarium look prettier, but you’re probably wondering if there are practical advantages of having them in there.

Here are the benefits we’ve found:

  • Provides your fish a healthier environment
  • The roots of the pearl grass clean water, unlike live plants that only build up algae
  • The plant emits oxygen, especially when the fish pearls on its leaves
  • Serves as a natural hiding spot and food for the fish or shrimp
  • Gives off a soothing vibe to the eyes and mind when looked at

Pearl grass is practically a plant pet with all the maintenance you have to do for it. As we’ve alluded to over and over in this article, it’s worth it as they create a more natural habitat for the fish.

Hemianthus micranthemoides allows your aquatic pets to be more active, and that conditions their systems to be stronger. You don’t want them dying on you in just a few months, after all.

Also, we have to admit that no aquarium looks complete without any pearl weeds for the fish to hide in. Taking care of these plants also make a good morning activity to get you going for the whole day, so they’re not only for your swimmy friends.

Photos from Tropica.

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