Integrating terrestrial plants into an aquarium setting, a practice often seen in modern aquascaping, creates a visually striking and unique environment. This technique bridges the gap between the aquatic and terrestrial worlds, mimicking the natural transition zones found along riverbanks and wetlands. The use of certain resilient species offers functional benefits by helping to naturally filter the water column. Success depends entirely on understanding a plant’s biological limits and employing precise setup methods.
The Biological Barrier to Submerged Growth
True terrestrial plants are structurally and physiologically unsuited for long-term, fully submerged life due to fundamental differences in gas exchange. Their leaves are covered in a thick, waxy cuticle designed to prevent water loss to the air, which severely restricts the uptake of dissolved gases when submerged. This protective layer becomes a barrier, hindering the necessary exchange of carbon dioxide and oxygen with the surrounding water.
The diffusion rate of gases in water is approximately ten thousand times slower than in air, making the acquisition of carbon dioxide for photosynthesis extremely difficult for land-adapted leaves. Terrestrial plants primarily rely on specialized pores called stomata to absorb gaseous carbon dioxide from the atmosphere. When fully underwater, these stomata become non-functional, and the plant cannot efficiently access the carbon it needs to survive.
Aquatic plants, conversely, have evolved thinner cuticles or none at all, and some utilize bicarbonate dissolved in the water as a carbon source. Terrestrial species generally lack this crucial mechanism. When oxygen cannot be delivered to the roots because air pockets in the soil are displaced by water, the roots effectively “drown,” leading to cellular damage and eventual plant death.
Common Terrestrial Plants Used in Aquariums
The terrestrial plants that succeed in an aquarium environment thrive only when their roots are submerged and their foliage is kept above the water line. These species possess a natural tolerance for high moisture or are commonly grown hydroponically, making them ideal for the emersed setup. A popular choice is Pothos (Epipremnum aureum), which rapidly develops extensive root systems that efficiently absorb nitrates directly from the water.
The Peace Lily (Spathiphyllum) is another common houseplant adapted for this use, provided its crown and leaves remain entirely out of the water. Its ability to tolerate low light conditions makes it suitable for tanks that are not intensely lit. Certain species of Dracaena can also survive with submerged roots, but their leaves must be kept in the air to prevent rot.
Even common house ferns, like the Boston Fern (Nephrolepis exaltata), can be used by resting the root ball on an elevated surface with the roots dangling into the water. These plants are highly effective at nutrient export, which helps maintain water quality and inhibit algae growth. They function as large, natural filters, pulling nutrients like nitrate that would otherwise fuel algae.
Essential Preparation and Safety Protocols
Introducing any plant from a nursery or garden center requires preparation to ensure the safety of aquatic livestock. The first step is the complete removal of all soil, potting medium, and rockwool from the plant’s roots. This material often harbors harmful bacteria, fungus, or decaying organic matter that can pollute the tank water.
A major safety concern is the presence of systemic pesticides, commonly used in commercial horticulture. These chemicals are designed to be absorbed by the plant and can leach into the aquarium water, proving highly toxic to fish, shrimp, and other invertebrates. Since the chemicals are inside the plant tissue, a simple rinse is insufficient.
To mitigate this risk, the roots must be rigorously rinsed and scrubbed under running water after removing all soil. A quarantine period of two to three weeks is highly recommended, placing the plant in a separate container of water changed daily. This process helps leach out any residual pesticides or fertilizers before the plant is introduced to the main aquarium environment.
Understanding Emersed Versus Submerged Placement
The distinction between emersed and submerged placement is the most important factor for success when using terrestrial plants. A fully submerged plant is entirely underwater, a condition fatal to land-based species due to gas exchange failure. In contrast, an emersed setup means the roots are submerged in the water column while the stem and all foliage are positioned above the water line, exposed to the air.
This emersed application is the only viable method for incorporating terrestrial plants. It allows the roots to absorb dissolved nutrients like nitrates from the tank, while the leaves access atmospheric carbon dioxide. Common setups involve suspending the roots from the top of the tank, placing the plant in a hang-on-back filter, or utilizing a specialized rim planter.
The water level must be carefully maintained to ensure the crown of the plant, where the leaves meet the stem, remains dry to prevent rot. This method capitalizes on the plant’s ability to pull nutrients from the water, which is highly beneficial for water quality. This setup transforms a common houseplant into a highly functional component of the aquarium’s filtration system. For hobbyists, this technique offers a low-maintenance way to export excess nutrients and create a captivating display that extends beyond the water’s surface.