Freshwater Dolphin (Marcusenius sp.)

Introduction

The Freshwater Dolphin, scientifically known as Marcusenius sp., is a unique and fascinating fish native to tropical Africa. It is named for its dolphin-like body shape and behavior, particularly its streamlined body and the way it moves through the water. While not as commonly seen in aquariums as other species, it is a sought-after species by fish enthusiasts due to its interesting characteristics and relatively rare availability in the aquarium trade. This species is known for being an elusive, nocturnal swimmer that thrives in well-established aquariums with ample space.

Scientific Name

Marcusenius sp.

Common Name

• Freshwater Dolphin

• Marcusenius (as a group, the specific species may vary)

Water Quality and Temperature

The Freshwater Dolphin thrives in clean, well-maintained water with stable parameters. They are sensitive to poor water quality, so regular water changes and proper filtration are essential for their health.

• Temperature: 75°F – 82°F (24°C – 28°C)

• pH Level: 6.5 – 7.5 (slightly acidic to neutral)

• Hardness: 5 – 15 dGH (moderately soft to moderately hard water)

• Filtration: Strong filtration is needed to keep water clean and oxygenated. They are used to flowing waters, so providing gentle water movement is beneficial.

• Water Changes: Perform regular water changes, 20-30% weekly, to maintain water quality.

Feeding

The Freshwater Dolphin is carnivorous, with a diet focused primarily on protein-rich foods. They are considered predatory and will hunt smaller invertebrates in the wild. In an aquarium, they should be provided with a balanced diet that mimics their natural feeding habits.

• Preferred Diet:

  • High-quality live or frozen foods, such as bloodworms, brine shrimp, daphnia, and small fish.

  • Pellet foods designed for carnivores

  • They can also accept some vegetable-based foods, but their diet should primarily consist of protein

• Feeding Frequency: Feed them once or twice a day, offering as much as they can eat within 3-5 minutes.

Tank Mates

Freshwater Dolphins are relatively peaceful but can be territorial, especially with smaller fish. Due to their nocturnal behavior, they may not interact with tank mates much during the day. However, it’s important to choose peaceful tank mates that can thrive under similar conditions.

• Compatible Tank Mates:

  • Larger, peaceful fish like catfish, larger tetras, and peaceful cichlids

  • Other slow-moving or nocturnal species

  • Snails and larger Shrimp

• Avoid:

  • Aggressive or fast-moving fish, such as many species of barbs or some types of cichlids, which may outcompete them for food or harass them

Substrates and Tank Decorations

The Freshwater Dolphin appreciates a well-planted tank with areas for hiding. While they do enjoy open swimming areas, they also benefit from having plenty of rocks and plants to retreat to. A substrate that allows them to burrow and hide will help mimic their natural environment.

• Substrate:

  • A fine gravel or sandy substrate is ideal, as they can burrow and move around freely.

• Tank Decorations:

  • Rocks, driftwood, and dense plantings will create hiding spots and mimic their natural habitat in African rivers and lakes.

  • Creating a tank with a dark substrate and subdued lighting will also help the Freshwater Dolphin feel more comfortable.

Suitable Plants

Plants are important for the Freshwater Dolphin’s environment, as they provide shelter and contribute to the overall water quality.

• Best Plant Choices:

  • Anubias

  • Java Fern

  • Amazon Sword

  • Vallisneria

  • Floating plants like Water Sprite for additional cover and a natural look

Sexing

Sexing Freshwater Dolphins is challenging, as they are relatively small and not sexually dimorphic (meaning males and females look very similar). Often, it is easier to differentiate between sexes when they reach sexual maturity, but even then, distinguishing them visually can be difficult without close observation.

• Males tend to be slightly smaller and more slender.

• Females are generally larger and rounder, particularly when carrying eggs.

Breeding

Breeding Freshwater Dolphins in captivity is challenging, and they are considered difficult to breed due to their specific environmental needs. They require a well-established aquarium with stable, mature water conditions to encourage breeding behavior.

• Breeding Conditions:

  • Freshwater Dolphins are egg layers and prefer dark, sheltered spots to lay their eggs.

  • Providing plenty of hiding spots and a slightly acidic water environment can help trigger breeding behavior.

  • Like many species in the family, they may scatter eggs on rocks or plant leaves.

• Fry Care:

  • Fry will hatch after a few days, depending on the temperature and water conditions.

  • Once hatched, they should be fed fine foods like liquid fry food, freshly hatched brine shrimp, or crushed flakes.

Maximum Size and Longevity

• Size: Freshwater Dolphins typically grow to a maximum size of about 6 to 8 inches (15-20 cm).

• Lifespan: They can live up to 5-7 years in ideal aquarium conditions with proper care.

General Information

Freshwater Dolphins are relatively shy, nocturnal fish that prefer to swim in areas with plenty of cover. They are not particularly social with other fish during the day, but at night, they are more active and may swim around the aquarium. These fish do best in species-specific tanks or with other peaceful, large species that can tolerate similar water conditions. They are not very aggressive but can become territorial if they feel threatened.

A Fun Fact

Despite being called “Freshwater Dolphins,” they are not actually related to marine dolphins. The name comes from their similar appearance, particularly their body shape and streamlined movements in the water, which resemble that of a dolphin!