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Author: Majid Ali

Title:  The Trouble with Planaria Worms?
Summary: Planaria worms are tiny, thin, milky white, parasitic worms which can appear in tanks that are overfed and when ammonia levels rise. A discussion of how to eliminate them.
Contact for editing purposes:
email: Editor, Ryedale Reporter:

Date first published: March 2003
Publication: Ryedale Reporter, Ryedale Aquarist Society, Yorkshire, England
Reprinted from Aquarticles:
Sept. 2005: Posted by Mike Talbot, of England, as part of the database of his msn group: africanriftlakecichlids.
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Printed publication:
Mail two printed copies to:
David Marshall,
16 Potter Hill,
North Yorkshire
YO18 8AA
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Vancouver, British Columbia
V6M 3W6


By Majid Ali
Adapted from an article which first appeared in the March 2003 edition of Ryedale Reporter Magazine, Ryedale Aquarist Society, Yorkshire, England

On many occasions fellow aquarists have sought my advice on 'infestations of aquatic parasites' which have suddenly appeared in their aquaria. Upon further investigation these infestations have, thankfully, proved to be of a harmless planarian nature.

Planarian worms are tiny, thin and milky white in appearance. They are distantly related to flukes, and some of these worms have been implicated in skin slime problems with marine fish. They are usually seen slowly gliding over the surfaces of the tank, surfaces of the glass and under the lid of box filters.

These particular worms are, at times, a problem. How do they manifest? They usually become visible when:-
1. An aquarist has overfed his/her fish.
2. The aquarium gravel is not hoovered accordingly.
3. Aquarium ammonia levels have risen.

If present in small numbers Planaria can be dealt with by eliminating the above, but when larger numbers are involved they become a problem. I have tried the following methods to try to clear them:-
a) I have used a variety of white spot cures, tonic salts and aquatic bacteriacides etc. without any real success. Fellow aquarists have claimed some success using Sterazin (Waterlife product), Anti-crustacean Parasite (Interpet) and Parasite Guard (Sera) but I have yet to try these particular products myself.
b) Sometimes removing the fish/aquatic livestock and raising the tank temperature, for 24 hours, to 35 C can rid a tank of Planaria.
c) Drastic - but strip the tank down, boil any gravel and scrub the decor clean, and leave everything to dry for a week (remembering to change any filter material). Unfortunately there is no guarantee that once the tank is re-established the problem may not quickly resume. A second strip down and washing with a bleach solution may be the answer?
d) Natural predators may help. Apple Snails, Hong Kong Plecs. (coldwater), Whiptail Catfish, and any Limnivorous Catfish (Mud-eaters, e.g. Twig Catfish and Bubble-nesting Catfish, who are constantly searching throughout the tank for vegetable matter, detritus, micro-organisms and tiny crustaceans), are among the species that will (usually if left unfed for a few days) eat away at Planaria on a long term basis. In the short term Betta and Pelvicachromis (Kribs.) species will eat small amounts of Planaria.

Please note that Planarian worms can get into the gills of aquatic livestock and cause irritation, leading to fish etc. becoming jumpy and starting to scratch against the decor. I have witnessed this with Axolotls, and when a friend's Red Cap Oranda was constantly rubbing against the decor with no signs of a disease infection. We ultimately discovered that an abundance of Planaria in the tank had caused this problem.

As we touched on earlier, Planaria can be a problem with filtration equipment, particularly of the box and Fluval type varieties. To rid such equipment of Planaria try one of the following:-
1. Strip the filter and give it a good scrub.
2. Pour boiling water in and on the filter (especially through the holes).
3. Immerse the filter in hot water which contains a mild solution of bleach.

Warning - Research carried out by Tim Henshaw at Bolton Museum (Lancashire, U.K.) indicates that Planaria carry a toxin on their surface. This toxin is particularly potent towards any species of shrimp and glass shrimp.

As Planaria are parasitic, can they harm humans who come into contact with them? As far as my research indicates there are no recorded cases, but always make sure that you wash your hands well following contact and that any cuts etc. are covered prior to work with Planarian problems.

I hope you have enjoyed this article. If you can add any information, particularly on livebearing fish which may eat Planaria, please contact David (via the contact details above) who will feature any 'Feedback' in a future issue of Ryedale Reporter (mailing you a writer's copy in return), as we still have much to learn about these and many other parasites, who our 'fish friends' have to contend with in aquaria.