How to remove harmful planarians from a reef aquarium?

There are several kinds of planarians (red, brown, etc.). The most dangerous are the red planarians Convolutriloba retrogemma.

Manual method

Remove the planarians regularly by siphoning (belling).

Biological method

The effectiveness of biological control is uncertain because it depends on the type of planarian and the environment of the aquarium. Commonly used predators are (choice of the species to adapt to the aquarium population):

• Nudibranch: Chelidonura varians (hammerhead nudibranch, toxic species);
• Fish: Pseudocheilinus hexataenia, Halichoeres chrysus, Halichoeres marginatus, Macropharyngodon ornatus, Macropharyngodon bipartitus, Synchiropus picturatus …

Chemical method

If the previous methods have not worked, you can consider using a medication (delivery only on veterinary prescription). Classically, the dosage is 0.5 mg of levamisole per liter of water to be treated (0.5 ppm), or 0.5 mL of the specialty Lévisole injectable 10% per 100 liters (presented in a 250 mL bottle).

This treatment is not without risk if it is carried out incorrectly. Because of the toxins released by dead planarians, certain aquarium organisms can also succumb: spirographs, even corals!

Preparation

• Prepare sufficient new sea water in anticipation of a major water change;
• Calculate the volume of water to be treated (filtration included, decorations excluded);
• Recover new activated carbon (contained in a nylon stocking), at a rate of at least 150 g per 100 liters of water;
• Clean the skimmer;
• Remove the chemical filter masses but let the filtration run;
• Manually eliminate as many planarians as possible by siphoning (less toxins released).

Carrying out the treatment

• H0: add the necessary quantity of levamisole directly into the aquarium water;
• H+2 hours: add the activated carbon to the filtration (the water is tinted orange);
• H+4 hours: eliminate the planarian corpses by siphoning;
• H+6 hours: carry out a major water change;
• H+24 hours: remove the activated carbon from the filtration.

Repeat this treatment if necessary at the end of a few days if any planarians survived.