Planarians

Flatworms that infest freshwater and marine aquariums. In freshwater aquariums they threaten shrimp colonies. In marine aquariums they attack corals.

Detailed explanation

Planarians are flatworms (Platyhelminthes) found in both fresh and marine water. They are predators or parasites depending on the species and can become a serious problem.

In freshwater aquariums the most common planarians are small (2-5mm), white or brown, and move by crawling on glass and surfaces. In aquariums with shrimp they are dangerous: they prey on the eggs, the young and can also attack newly mutated adults (when the shell is still soft).

Treatments in freshwater aquariums include planarian traps (a container with food inside and holes that allow entry but not exit), fenbendazole (Panacur, veterinary pesticide) and No Planaria (a commercial product made from betel nut extract). Warning: fenbendazole can kill snails.

In marine aquariums, flatworms (Convolutriloba retrogemma, AEFW, Acropora Eating Flatworm) are a scourge for SPS corals. Red Flatworms (Convolutriloba) multiply on glass and rocks and compete with corals for light. AEFWs live under the Acropora eating the tissue from below.

Marine treatment includes Flatworm Exit (Salifert) for red flatworms (with caution: mass death of flatworms releases toxins). For AEFW corals are dipped in CoralRx or Bayer.

Prevention is the key: inspect and despatch any new coral before introducing it to the aquarium. Nudibranchs Chelidonura varians eat red flatworms but are short-lived.

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