THE TROUBLE WITH PLANARIA WORMS?
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
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.