Integrating terrestrial houseplants into or adjacent to an aquarium system is known as riparium or paludarium keeping. This method involves allowing a land-based plant’s roots to grow directly into the tank’s water while keeping the foliage above the surface. Enthusiasts adopt this technique for both its distinctive aesthetic appeal, creating a lush, jungle-like transition zone, and its practical ecological benefits. This symbiotic relationship establishes a more complex, natural ecosystem.
Why Integrate Houseplants with Aquariums
The primary functional benefit of adding houseplant roots to an aquarium is their effective role in water quality management. Terrestrial plants are far more efficient at nutrient export than many fully submerged aquatic plants because their leaves have access to unlimited atmospheric carbon dioxide. This access allows for rapid growth, which demands a constant supply of nutrients drawn directly from the aquarium water.
These plants act as natural biofilters, aggressively consuming excess nitrogen compounds, specifically nitrates. High nitrate levels can stress fish and fuel undesirable algae growth; by absorbing these compounds, the plants stabilize the water chemistry and reduce the frequency of necessary water changes. Beyond filtration, the dense root structures provide enrichment for the tank inhabitants, offering shelter and hiding places for smaller fish and fry.
Essential Preparation and Safety Checks
Before introducing any houseplant to an aquatic environment, meticulous preparation is necessary to ensure the health and safety of the tank inhabitants. The first step is the thorough removal of all the original potting substrate, as soil can pollute the water and introduce unwanted organic material. Roots must be gently but completely cleaned under running water to dislodge every particle of dirt or growing medium.
A significant risk comes from chemical residues, particularly systemic pesticides, which are designed to be absorbed by the plant and can be deadly to sensitive aquatic life like shrimp. Plants from nurseries should be considered contaminated and must undergo a quarantine process, as simple rinsing will not remove internal chemicals. The safest protocol is to quarantine the plant cuttings or bare roots in a separate container of water for three to four weeks, performing full water changes daily. This lengthy process helps leach out any residual systemic chemicals before the roots are submerged into the main aquarium system.
The plant must then be suspended so that only the root mass is in the water, ensuring the crown and all foliage remain entirely dry and above the waterline. Specialized aquarium plant holders, clips, or DIY solutions like small net pots are used to secure the plant to the tank rim or filter intake. This placement is necessary to prevent the plant from rotting and polluting the water.
Houseplants Suitable for Root Submersion
A select group of common houseplants thrives in this semi-aquatic setup, readily adapting to water culture and displaying excellent nutrient uptake capabilities.
- Pothos (Epipremnum aureum), often called Devil’s Ivy, is easy to root from cuttings and exhibits a rapid growth rate, making it a highly effective nitrate absorber.
- Various Philodendron species, especially the vining types, also perform well, sharing the Pothos’s ease of care and willingness to grow extensive root systems in water.
- The Peace Lily (Spathiphyllum) is frequently positioned so its roots are submerged in a hang-on-back filter where water flow is consistent. These plants develop a thick, fibrous root structure that provides ample surface area for beneficial bacteria colonization.
- Spider Plants (Chlorophytum comosum) can also be used effectively, particularly the “pups” that form on runners, which root quickly in water. However, they may not tolerate long-term submersion as well as the vining aroids.
The key to success is providing adequate light to the foliage above the tank, as brighter conditions encourage the rapid growth necessary for high nutrient consumption. Anchoring the roots can be achieved by gently wedging them into the filter intake, using suction cup-mounted holders, or employing small mesh cups filled with inert media like lava rock or clay pebbles for stability.
Toxic Varieties and Placement Missteps
While many terrestrial plants are safe for the riparium method, certain common houseplants contain compounds that pose a risk to the aquatic environment. A significant number of popular indoor plants, including Pothos and Peace Lilies, contain insoluble calcium oxalate crystals, which are generally not a danger to fish because the compounds do not readily dissolve in the typical freshwater pH range. The greater concern lies with plants that contain water-soluble toxins or those that are highly irritant, such as Dumb Cane (Dieffenbachia).
The most common danger to the aquarium ecosystem comes from improper placement that leads to plant decomposition. True terrestrial plants, such as succulents, most ferns, and African Violets, are not adapted to have wet roots and will quickly rot if submerged. Even suitable plants will rot if the stem or crown is submerged, leading to a dangerous spike in organic waste. This rapid decay releases high amounts of ammonia and other pollutants, rapidly degrading water quality and risking the lives of fish and invertebrates. Constant monitoring is necessary to ensure only the roots are in contact with the water.