Have you seen mondo grass being sold as an ‘aquatic plant’ in your local pet store? You may even be one of the unlucky ones who bought it, thinking it’ll be an easy plant to grow in your aquarium.
The not-so-good news is that mondo grass isn’t really an aquatic plant at all, and can only be persuaded to grow in water under very specific conditions. While mondo grass is an excellent house and garden plant, there are several grass-like plant species that are much better for fish tanks!
In my research, I discovered it might not even be safe for pets. Let’s learn more about mondo grass and its alternatives!
What Is Mondo Grass?
Ophiopogon japonicus (aka. dwarf lilyturf, mondo grass, fountain plant, monkey grass, dragon’s beard, snake’s beard) is a grass-like evergreen perennial that’s native to China, India, Japan, and Vietnam. Despite its name, mondo grass is not really a grass at all – it’s more closely related to lilies!
Although it is occasionally sold for aquariums, mondo grass is better known as a garden or house plant. It’s useful for creating lawns, especially in shady areas. Gardeners enjoy mondo grass for its white flowers and purple-black berries.
A word of warning – mondo grass is so prolific in warm climates that it’s considered an invasive weed in the Southern United States!
Is Mondo Grass Suitable for an Aquarium?
Since it’s most famous as a garden plant, then why is mondo grass marketed as an aquarium plant?
That’s what many fish keepers are asking, especially those who have bought the plant and only later done their research!
The answer is, it is just about possible to keep mondo grass underwater, but it is very difficult!
Mondo grass is chiefly a plant for dry land, although it seems to be naturally adapted to life underwater for short periods of time. Perhaps it evolved this way to cope with the annual monsoons in the Asian countries that it comes from.
How Do I Keep Mondo Grass Alive Underwater?
In general, mondo grass will survive for around one month underwater before beginning to die and rot. There are rumors that some forms of this plant such as the dwarf variety ‘Kyoto dwarf’ can survive underwater for longer periods than others.
Even so, it is still a challenge to keep this plant healthy when fully submerged, and some aquatic plant enthusiasts have come up with some methods to keep mondo grass alive for longer underwater. Some claim that, once established, mondo grass can even live indefinitely underwater!
If you want to give it a shot, these methods should give you your best chances:
Submerge Mondo Grass Slowly
Because life underwater isn’t this plant’s natural habitat, it’s a good idea to submerge it gradually. Some aquarists advise that you should submerge the plant for a few days, followed by a few days above water, and repeat this cycle until the plant is growing strongly.
Gradually give the plant more and more time underwater until it seems happy to live there full time.
Provide Ideal Growing Conditions for Mondo Grass in Your Aquarium
Some hobbyists who have managed to keep mondo grass underwater for longer periods claim that the plant likes relatively cool aquarium water temperatures of 65-75°F.
Clean water with low light levels and no fertilization is recommended. Since this plant is better adapted to live above water, then good gas exchange in the aquarium will likely play a key role in its survival.
You can increase gas exchange by using a filter with a high circulation rate, and an aquarium spray bar or filter baffle that increases surface agitation and oxygenation at the water’s surface.
What to do if Your Mondo Grass Is Dying?
If you manage to keep mondo grass alive in your aquarium for several months, then give yourself a pat on the back! That’s longer than most aquarium owners have managed.
If your plant does eventually begin to wither and melt, however, you have two options:
Option A is to attempt to revive your mondo grass by offering it conditions closer to those suggested above. Unfortunately, since the plant is so fussy underwater, this won’t always be easy. The low lighting, low temperatures, and high water flow might not necessarily be compatible with your other plants and fish.
Option B is to remove the plant before it rots and fouls the water. If your mondo grass is clearly on its way out, it’s better to remove it from the aquarium before it begins rotting and dirtying the water with ammonia. Dying and dead plant material are a major cause of poor water quality and algae blooms in aquariums so it’s better to remove it promptly!
Can I Grow Mondo Grass in a Terrarium?
In case you didn’t know, terrarium is the correct term for tanks that just host plants, whereas vivarium is the name for a tank that includes dry land reptiles. Ripariums and paludariums are tanks with part land and part water and may also include amphibians and reptiles.
The great news is that all of these types of tanks are much more suitable for growing mondo grass than aquariums! The more of the plant that’s above water, the more likely it’ll survive – especially if its crown is above the water line.
Mondo grass will grow well in sealed, humid terrariums as well as open, drier setups. As long as it receives regular watering, it should prove to be a hardy plant.
Can I Grow Mondo Grass in a Container?
As well as performing well in terrariums, mondo grass is an excellent plant to grow in pots. Whether you keep it inside or outside your house, mondo grass is a pretty and tidy little plant that rarely exceeds 5 inches in height.
It’s also a very tough plant species that has no problem with temporary waterlogging, but interestingly, it’s drought-tolerant, too! You can read more about growing mondo grass in pots and containers here.
Is Mondo Grass Safe for My Pets?
Mondo grass is usually listed as being safe for pets, but after hearing that the roots contain saponins, I decided to look into the question more deeply.
A scientific study from 2019 in China confirms that the roots of mondo grass contain high levels of steroidal saponins. Since saponins are used in the treatment of certain ailments, they may account for the mondo grass’s reputed medicinal benefits, including its use in Traditional Chinese Medicine.
But some types of steroidal saponins are highly toxic to animals, including cats, dogs, reptiles, and fish. Cats and dogs have been poisoned before by eating parts of the Dragon Tree (Dracaena marginata) that contain a similar type of saponin, so I wouldn’t rule it out as a potential danger.
In my research, however, I didn’t come across any direct reports of mondo grass poisoning animals.
Some Better Alternatives to Mondo Grass for Aquariums
If you’re after some grass-like plants for your fish tank, worry not! There are many other candidates that are just as beautiful and much easier to grow than mondo grass.
Sagittaria subulata (Dwarf Sag), Lilaeopsis novae-zelandiae (Micro Sword), Echinodorus tenellus (Dwarf Chain Swords), and Eleocharis acicularis/Eleocharis parvula (Dwarf Hairgrass) are all excellent choices and much more beginner-friendly than mondo grass!
All four of these live plants are included in our dedicated article on the best aquarium grasses.
Mondo grass is not a true aquatic plant and is very difficult to grow in an aquarium. Although some aquarists have had some limited success getting it to grow under specific conditions, it is generally much better kept as a houseplant or in your garden.
The good news is that there are many other grass-like plants for aquariums that don’t need your constant attention to stay alive!