SAN PABLO CITY, Philippines (July 2026) — A brightly colored aquarium fish once prized by hobbyists is now causing growing concern in Laguna, where researchers say it has become firmly established in Lake Sampaloc and is threatening native wildlife while potentially posing public health risks.
Researchers from the Ateneo de Manila University Department of Biology and the Ateneo Aquatic and Fisheries Resources Laboratory found that the ornamental Flowerhorn cichlid (Amphilophus spp.) has evolved from an escaped aquarium species into one that is now part of both the lake’s ecosystem and local aquaculture.
The study found that the fish’s continued presence is no longer accidental. Beyond surviving in the wild after reportedly escaping during a major typhoon, Flowerhorn cichlids are now intentionally retained and sold, allowing their population to persist and spread.
A growing threat to native fish
The researchers warn that Flowerhorn cichlids are aggressive and highly territorial, often taking over breeding and feeding areas that native fish depend on.
One species already feeling the pressure is the ayungin (Leiopotherapon plumbeus), a freshwater fish once commonly found in the lake. The species is now considered Vulnerable by the International Union for Conservation of Nature (IUCN) and has become increasingly difficult to find in Lake Sampaloc.
The invasive fish also thrives in polluted environments. Researchers said its ability to adapt allows it to survive in waters affected by nutrient runoff, untreated sewage, household waste, microplastics and contaminants associated with aquaculture.
Possible public health concerns
Beyond ecological damage, the study highlights potential health concerns linked to the invasive species.
Previous research has shown that Flowerhorn cichlids can carry Paracapillaria philippinensis, a zoonotic parasite capable of infecting humans. The parasite can cause intestinal capillariasis, a disease associated with abdominal pain, chronic diarrhea and malnutrition.
Lead author Hannah Nicole C. Gasmen said the species may serve as a reservoir for parasites, pathogens and contaminants, making it an important subject for future ecological, aquaculture and public health research.
Turning an invasive fish into a resource
Instead of simply removing Flowerhorn populations, the researchers propose exploring a circular economy approach by converting harvested fish into aquafeed.
They stressed that any harvested biomass should first undergo screening for parasites, contaminants and microbiological safety before being used.
The study also recommends using the Aquatic Species Invasiveness Screening Kit (AS-ISK), a risk assessment tool previously applied to non-native freshwater fish in Lake Naujan. Researchers believe applying the same screening method to Lake Sampaloc and other Philippine lakes could help authorities identify invasive species earlier and develop more effective management strategies.
Gasmen emphasized that protecting the country’s freshwater ecosystems will require cooperation among local communities, researchers and policymakers.
The findings were published in the March 2026 issue of World Aquaculture in the paper titled Fenced and Feral: Farming and Spread of Flowerhorn (Amphilophus spp.) in Lake Sampaloc, Philippines by Hannah Nicole C. Gasmen and Dr. Janice A. Ragaza.
