The 10 Worst Aquarium Plants You Can Buy
Guest Post By Jino S. T.
Cambomba Caroliniana – Number 10 of the 10 worst aquarium plants
How to tell if you’ve purchased one of the 10 worst aquarium plants
Picture this: You’re standing in front of your beautifully arranged aquarium, admiring the careful balance of fish, decorations, and plants you’ve cultivated over months. Then you notice something isn’t quite right. That innocent-looking plant you added last week has somehow quadrupled in size, choking out your other plants and clogging the filter. Your pristine aquascape is quickly becoming an underwater jungle, and not in a good way.
This scenario plays out more often than you might think in the aquarium hobby. While aquatic plants can transform a tank into a stunning underwater garden, some species are nothing short of aquatic menaces. These botanical troublemakers can rapidly overtake an aquarium, alter water chemistry, harm fish, and prove nearly impossible to eliminate once established.
The problem isn’t just aesthetic. Problematic aquarium plants can impact every aspect of your tank’s ecosystem. They can block essential light from reaching other plants, deplete vital nutrients, interfere with equipment functionality, and even alter oxygen levels. Some species are so invasive that they’re banned in certain regions, and for good reason – escaped aquarium plants cause millions of dollars in environmental damage to natural waterways each year.
What makes identifying these problematic plants particularly challenging is that many are still widely available in the aquarium trade. Some are even marketed as “beginner-friendly” or “oxygen-generating” species, despite their potential to become aggressive invaders. Others might appear manageable in store display tanks but reveal their true nature once established in home aquariums.
In this comprehensive guide, we’ll explore the ten most problematic plants you should never add to your aquarium. From the deceptively cute duckweed to the aggressively spreading Brazilian waterweed, we’ll examine why these plants earned their place on the “worst of” list and why even experienced aquarists avoid them.
Hygrophila polysperma (Indian Swampweed): The Fast-Growing Menace
Image above: Indian Swamp Weed (Hygrophila polysperma)
If you’ve been in the aquarium hobby for a while, you’ve probably heard whispers about Indian Swampweed. While it looks harmless with its bright green leaves and compact growth, this plant has earned its reputation as one of the most problematic aquarium plants you can get.
What Makes It Terrible
In optimal aquarium conditions (which aren’t hard to achieve), this plant grows at a rate that is hard to believe. We’re talking about 2-2.5 cm of new growth every single day, with stems that can reach lengths of over 2 feet. But the growth rate isn’t even the worst part.
The plant has developed several highly effective strategies that make it a nightmare to control. Each node (the points where leaves meet the stem) can develop roots, and every single fragment, no matter how small, can develop into a new plant.
It grows both underwater and above water, even growing out of your tank if given the chance. The stems constantly produce side shoots, creating dense bushes that take over entire sections of your aquarium.
Perhaps most surprisingly, it can flower and produce viable seeds even when fully submerged, giving it yet another way to spread.
To give you a real sense of scale: a single 6-inch stem can turn into dozens of plants within a month. The plant doesn’t just grow upward – it spreads sideways, creates runner stems along the substrate, and sends shoots in every direction. Even in low-light conditions or with poor nutrients, it continues to grow, just at a slightly slower pace. Its ability to adapt to almost any water parameters or lighting conditions means there’s virtually no aquarium where it won’t thrive and eventually become a problem.
The Legal Issue
Here’s something most hobbyists don’t realize until it’s too late: Indian Swampweed is actually illegal in many countries, including the United States. It’s been classified as a federal noxious weed because of how easily it escapes into local waterways and causes environmental damage. In places like Florida and Texas, it’s already created significant problems in natural ecosystems.
The Bottom Line
While it might seem like an attractive, fast-growing plant for your aquarium, the combination of its aggressive growth, near-impossible removal, and illegal status in many areas makes Indian Swampweed a plant you should absolutely avoid. Trust me, there are plenty of other beautiful, fast-growing plants that won’t take over your tank or potentially get you in trouble with the law.
Additional Information
Hygrophila polysperma (Roxb.) T. Anders. (PDF)
https://species.wikimedia.org/wiki/Hygrophila_polysperma
A better choice
Image below: Hygrophila pinnatifida – Tap image to buy.
Salvinia molesta (Giant Salvinia): The Surface Invader
If you’re looking for a floating plant that’ll make you regret every life decision that led you to aquarium keeping, Giant Salvinia is your plant. This floating fern might look delicate and attractive, but it’s earned its spot on this list through sheer aggressive growth.
What Makes It Terrible
Salvinia molesta earns its reputation through unprecedented growth rates and reproductive capabilities that have been extensively studied due to its environmental impact. In optimal conditions (temperatures between 20-30°C), a single plant can multiply into an 8-foot-wide mat in just three months. A small population can double its biomass in as little as 3-4 days, leading to surface coverage that increases exponentially.
The plant’s structure makes it particularly problematic in any aquatic system. Each plant consists of pairs of floating leaves connected by a submerged leaf that functions like a root. The upper surface of the floating leaves is covered in complex, water-repellent hairs arranged in an egg-beater pattern. This unique adaptation helps the plant stay afloat even in turbulent water and makes it resistant to mechanical removal – water simply rolls off the leaves, keeping them buoyant even when pushed under the surface.
The reproductive process is remarkably efficient: as the plant grows, it forms chains of connected plants that can reach up to 1 foot in length. When these chains break apart, each segment becomes an independent plant capable of starting its own colony. In aquarium conditions, where nutrients are plentiful and there are no natural predators, this growth pattern quickly leads to complete surface coverage. Even more concerning is its ability to survive in less than ideal conditions – when nutrients are scarce, the plant simply produces smaller leaves but continues to multiply, making it nearly impossible to control through nutrient limitation.
Environmental Impact
Giant Salvinia isn’t just a problem in home aquariums – it’s considered one of the world’s worst aquatic weeds. In natural environments, it forms such dense mats that boats can’t move through waterways, fish can’t surface for air, and native plants die from lack of light. It’s become such a problem that scientists have had to introduce special weevils in some areas just to control it.
The Bottom Line
Giant Salvinia is more than just an aquarium nuisance – it’s a serious invasive species that can quickly turn your tank into a maintenance nightmare. Its rapid growth rate, ability to block light, and tendency to degrade water quality make it a plant that should stay far away from your aquarium. Even if you’re an experienced aquarist, the risks far outweigh any potential benefits.
A better choice: Red Tiger Lotus
