Nematanthus ‘Black Goldfish Plant’ is a unique tropical houseplant admired for its glossy dark foliage and unusual goldfish-shaped flowers. Native to the tropical regions of South America, plants in the Nematanthus genus are commonly known as Goldfish Plants because their bright blooms resemble tiny swimming goldfish. The ‘Black’ variety is especially striking because of its deep green to almost black leaves, which create a dramatic contrast against the vivid orange flowers.
This plant has a trailing or slightly cascading growth habit, making it a popular choice for hanging baskets, shelves, or elevated planters where the stems can spill naturally over the edges. Under the right conditions, it can bloom multiple times throughout the year, producing clusters of bright orange tubular flowers that stand out beautifully against the dark foliage.
In this blog, you’ll learn everything you need to know about caring for the Nematanthus Black Goldfish Plant, including lighting, watering, humidity, soil, propagation, pruning, and tips for encouraging healthy growth and more blooms.
Image: @Jen PF
LIGHTING
Nematanthus ‘Black Goldfish Plant’ grows best in bright, indirect light, and proper lighting is one of the most important factors for keeping the plant healthy and encouraging frequent blooms. A location near an east- or south-facing window with filtered sunlight is usually ideal. Bright morning sun is often very beneficial because it provides enough energy for flowering without exposing the leaves to the harsher heat of the afternoon.
Although this plant enjoys bright conditions, intense direct afternoon sun may scorch the leaves or cause stress, especially during hot summer months. Burned leaves may develop pale, dry, or brown patches that do not recover. On the other hand, insufficient light can cause the stems to become stretched and leggy as the plant grows toward the nearest light source.
Low light also affects flowering significantly. The leaves may lose some of their deep green or nearly black coloration, becoming lighter and less glossy over time. In many cases, a plant grown in dim conditions may continue surviving but produce very few flowers or stop blooming altogether.
Rotating the plant occasionally can also help maintain even growth, particularly for hanging baskets where stems naturally lean toward the light source. If natural light indoors is limited, using a grow light for several hours a day can help support healthier foliage and encourage more consistent flowering.
WATERING
Nematanthus ‘Black Goldfish Plant’ prefers lightly moist soil, but it does not tolerate constantly wet conditions. A good approach is to water thoroughly when the top layer of soil feels slightly dry to the touch. Water until excess moisture drains from the bottom of the pot, then allow the container to drain completely before placing it back in its decorative pot or tray. Pots with drainage holes are especially important because stagnant water around the roots can quickly lead to root problems.
Overwatering is one of the most common issues with the Black Goldfish Plant and may cause yellowing leaves, root rot, soft stems, or sudden leaf drop. In severe cases, constantly wet soil can weaken the roots enough to reduce flowering significantly. Heavy soil mixes that stay damp for too long can create similar problems even if watering frequency seems reasonable.
During spring and summer, when the plant is actively growing and flowering, it will usually need more consistent moisture. During cooler months or periods of slower growth, watering should be reduced slightly because the plant uses less water. It’s also helpful to avoid splashing excessive water directly onto the leaves and flowers repeatedly, especially in lower airflow conditions, as constantly damp foliage may increase the risk of fungal problems.
TEMPERATURE AND HUMIDITY
Nematanthus ‘Black Goldfish Plant’ prefers warm temperatures and generally grows best between 65 and 80°F. Cold drafts and rapid temperature fluctuations can stress the plant and may reduce blooming or cause leaf drop. Placing the plant too close to air conditioners, heaters, frequently opened doors, or cold windows during winter can create sudden changes that the plant dislikes. Temperatures below 55°F may slow growth significantly and potentially damage the foliage if exposure continues for too long.
Humidity is another important factor for maintaining healthy growth and encouraging flowers. Moderate to high humidity levels are ideal because dry indoor air can gradually cause problems such as crispy leaf edges, dull foliage, slowed growth, or fewer blooms. This is especially common during winter when indoor heating reduces humidity levels inside the home.
Image: @COULANGES
Using a humidifier nearby is often one of the most effective ways to maintain a more comfortable environment for the plant. Pebble trays filled with water or grouping tropical plants together can also help increase local humidity around the foliage. Bathrooms or kitchens with bright indirect light sometimes provide naturally higher humidity levels as well.
SOIL AND FERTILIZER
A light, airy, well-draining soil mix works best for Nematanthus ‘Black Goldfish Plant’ because the roots prefer a balance of moisture and airflow. Soil that stays too dense or wet for long periods can quickly lead to root problems, while a loose mix allows the roots to breathe properly and supports healthier growth and flowering.
African violet soil mixes or tropical potting blends combined with materials such as perlite, orchid bark, pumice, or coarse sand often provide the ideal balance of moisture retention and drainage. The soil should feel soft and airy rather than heavy or compacted. Orchid bark is especially helpful because it improves airflow around the roots while still allowing the plant to absorb enough moisture.
Containers with drainage holes are also very important. Even a well-draining soil mix can become problematic if excess water has nowhere to escape. Hanging baskets and breathable pots can help improve airflow and prevent excess moisture buildup around the roots.
Image: @TuktaBaby
During spring and summer, when the plant is actively growing and flowering, feeding with a diluted balanced liquid fertilizer every two to four weeks can help support healthy foliage and encourage more blooms. Fertilizers designed for flowering houseplants are often a good choice because they provide nutrients that support both leaf growth and flower production.
Reducing fertilizer during fall and winter is usually recommended because the plant naturally slows its growth during cooler months and requires fewer nutrients. Feeding too heavily during slower growth periods may create unnecessary stress on the roots.
TOXICITY
Nematanthus plants are generally considered non-toxic to cats, dogs, and humans, making them a relatively safe choice for pet-friendly homes. Unlike some tropical houseplants that contain irritating sap or harmful compounds, the Black Goldfish Plant is not commonly associated with serious toxicity issues.
However, it is still best to discourage pets or small children from chewing on the leaves or flowers. While the plant is considered low-risk, consuming large amounts of any plant material may still cause mild digestive discomfort such as vomiting or stomach irritation in sensitive pets.
EXTRA CARES
POTTING AND REPOTTING
Because of its trailing and slightly cascading growth habit, Nematanthus ‘Black Goldfish Plant’ looks especially attractive in hanging baskets, elevated planters, or decorative containers where the stems can spill naturally over the edges. Its glossy dark foliage and bright orange flowers become even more eye-catching when the plant is allowed to trail freely.
Choosing a container with proper drainage holes is very important because the plant does not tolerate soggy soil around the roots. Hanging baskets and breathable pots can also help improve airflow and prevent excess moisture buildup, which supports healthier root conditions over time.
Repotting is generally only needed every one to two years or whenever the roots begin to outgrow the container. Signs that repotting may be necessary include roots growing through drainage holes, soil drying out unusually quickly, slowed growth, or reduced flowering.
Unlike some houseplants that prefer large containers, the Black Goldfish Plant often blooms well when slightly root-bound. Because of this, moving the plant into a much larger pot is usually unnecessary and may even increase the risk of overwatering by allowing the soil to stay wet for longer periods. When repotting, it’s usually best to choose a new container only slightly larger than the current one.
The best time to repot is usually during spring or early summer when the plant is actively growing and can recover more quickly from root disturbance. After repotting, keeping the plant in bright indirect light with moderate watering can help it adjust more comfortably to its new container.
PROPAGATION
Nematanthus plants are relatively easy to propagate, making them a great choice for growers who want to expand their collection or create fuller hanging baskets. Stem cuttings are the most common and reliable propagation method, and healthy cuttings usually root fairly quickly under the right conditions.
To propagate the Black Goldfish Plant, select a healthy stem with several leaves attached and trim it just below a leaf node using clean scissors or pruning shears. Lower leaves can be removed to expose a small section of stem that will sit in water or soil. The cuttings can then be rooted either in water or directly in moist, well-draining potting mix.
Image: @TuktaBaby
If rooting in water, the water should be changed regularly to keep it clean and prevent rot. Once roots become established, the cuttings can be transferred into soil. For soil propagation, lightly moist soil is usually enough, but the mix should never stay overly wet.
Propagation is also a useful way to refresh older plants that may have become leggy or sparse over time. Trimming and replanting healthy stems can help create a fuller, bushier appearance while encouraging fresh growth.
PRUNING
Regular pruning helps Nematanthus ‘Black Goldfish Plant’ maintain a fuller, bushier appearance and encourages healthier branching over time. Without occasional trimming, the stems may gradually become long, sparse, or leggy, especially in lower light conditions. Pruning helps the plant stay more compact while improving its overall shape and balance.
Trimming leggy stems after flowering is especially beneficial because it stimulates fresh new growth from the nodes along the stems. As the plant branches more, it develops a denser trailing appearance that looks fuller in hanging baskets or decorative containers.
The best time for heavier pruning is usually during spring or after a major flowering cycle, when the plant can recover and regrow more quickly. Light trimming can still be done throughout the year whenever needed to maintain shape.
Using clean, sharp scissors or pruning shears helps avoid damaging the stems. Healthy cuttings removed during pruning can also be propagated easily, making pruning a convenient way to both refresh the plant and grow new ones.
COMMON PROBLEMS
Overwatering is one of the most common problems for Nematanthus ‘Black Goldfish Plant’ and can quickly lead to root rot, yellowing leaves, soft stems, or sudden leaf drop. Because the plant prefers lightly moist but well-draining soil, constantly wet conditions can weaken the roots and reduce flowering over time. Heavy soil mixes or pots without proper drainage often make the problem worse by trapping excess moisture around the roots.
Insufficient light is another frequent issue and may cause the plant to become stretched or sparse. In lower light conditions, the stems often grow longer with fewer leaves, and flowering may decrease significantly. The dark foliage may also lose some of its rich glossy appearance if the plant does not receive enough brightness.
Pests such as mealybugs, spider mites, and aphids may occasionally appear, particularly in warm, dry indoor environments. Mealybugs often hide near leaf joints and leave behind white cotton-like residue, while spider mites may cause tiny pale spots or fine webbing beneath the leaves. Aphids are more likely to appear around soft new growth or flower buds.
