This is more general information, which may or may not be of help or interest to jonny_dw or to anyone else, from a decided non-expert.
As you've been so sagely advised above, the planaria may be feeding on something else inside your tank - and if a regular gravel vac doesn't seem to help enough, you might try keeping a very close eye on any plants which may not be doing as well as could be hoped, as degenerating plant matter - including that under the substrate - can supply a food source not always considered.
I've had them several times come in on plants, this despite having started doing bleach dips, although I might have rendered that pointless by not leaving the plants in long enough.
And I've had a bad infestation of them, as well as several other things, hatch out of plants from an order which was dipped and quarantined for over a week - multiplying like crazy even in entirely animal-empty 'new' tanks which had never had any food added.
In that case, I wound up cleaning the tanks and starting over in all (luckily smaller, nothing over 15 gal.) three tanks, as one of the critters was a voracious plant-eater, and there wasn't much left to save.
But while some planaria also appeared in other, inhabited tanks to which I'd added plants from that order, I see very few, and those visible, at least, have diminished considerably from the number originally appearing.
In the new tanks, I'd had various plants abruptly turn brown/black and die, possibly from the attentions of the plant-eating critters at or near the roots, this rotting matter potentially supplying food for such creatures as planaria.
The point is that while planaria may multiply according to food source, it may not necessarily be due to food you're adding.
And while they generally are harmless, I have heard that they can enter a fish's gills and irritate the heck out of them, besides being toxic to shrimp and attacking eggs, including those on a berried female.
That given below was not one of my original sources of info, but neatly ties up a number of factors not normally considered - although what I term planaria, and often see identified as such, are white, worm-like critters seen on the glass in the light and may not be quite the same sort of thing.
However, they do belong to a very large family...)
http
/en.allexperts.com/q/Fish-1472/planaria.htm
'... Planaria are a free-living flatworm found in almost every kind of environment, on land and in fresh and salt water. They are a very small black or brown flatworm that look very similar to leeches and often appear in freshwater aquariums. They are generally around 3 to 5 mm long, but some grow as large as 10 mm. In a normal aquarium situation they usually don't cause any problems and probably even go unnoticed. However, if you get them in a breeding aquarium, they can destroy a whole spawning of eggs within hours. They are usually seen crawling around on the front of the aquarium after the lights have been turned off. They feed on anything organic but can also infect the mucous membranes of the fish's gills. They feed by sucking food into their gastrovascular cavity through a tube called the pharynx located on the mid-ventral surface.
'Planaria originated in Indonesia.
'You can get rid of planaria by treating the tank with Flubendazole 5 percent. Never squash or in any way dissect them, as each piece will become a new worm. ...'
Unfortunately, flubendazole is toxic to shrimp, but (with reference to hydra, planaria not specified)
http/www.planetinverts.com/forum/viewtopic.php?p=6316
'... I have found that a very small dose of Flubendazole can suppress Hydra blooms without killing the shrimp but it is a delicate balance. I would use only about 1/8 tsp/10 gal as the maximum dose if shrimp are present of the 5% flubendazole powder. ...'
I don't know if you or anyone else is having trouble with planaria (or planaria-like creatures - I have something similar which, oddly, suspend themselves from a thread, so don't know if this applies to my situation until I know what these critters are) in shrimp tanks or aquaria containing shrimp, but I'll add this, and also hope for input...)
Had some trouble (&%$#@*! puter) getting to an article giving very detailed experience of experimental use, so went to cached:
http/72.14.205.104/search?q=cache:wSP_cg...t=clnk&cd=4
Fish Fanatic's Blog - 'Planaria and Hydra Elimination in Shrimp Tanks
Published by fshfanatic September 15th, 2008 in Brackish Fish. .
'... All of my tanks had planaria in them and I had been assured by some local hobbyists that planaria were harmless to shrimp. I have since found this article: TheTrouble with Planaria, and have come to the conclusion that the planaria were indeed detrimental to my shrimp population. ...'
'... Fenbendazole is most easily found as a dog de-wormer and can be purchased at most pet supply stores. I used the “Safe Guard” brand labeled for dogs. Panacur is another brand name product that can be used. The price was about $14 for four 1 gram packs. This was the smallest size available at my local fish shop. Online information is “sketchy” at best for using this medication in aquariums. Some people describe using a “pinch” of the powder for their tanks or using a “BB” sized measuring spoon for their tanks. Most accounts do not give the volume of their tanks so figuring out a dosage from their information is next to impossible. The best information I could find suggested using a 2ppm dosage to de-worm fish. I was worried about the effects on shrimp with this dosage so I calculated a much smaller dosage for my shrimp tanks. According to the package, one gram of the powder contains 222mg of fenbendazole. Therefore, 0.1gm would contain 22.2mg and this would be about 0.6ppm (can someone please double check my math) dose for my 10 gallon tanks. ...'
'... Since shrimp can be very susceptible to most medications, shrimp only tanks can be can be very difficult to rid of pests. A 0.6 ppm dose of fenbendazole seems to be highly effective against both planaria and hydra in shrimp tanks and does not harm shrimp, snails, or other fauna, at this dosage. Four months have passed since first dosing fenbendazole in my shrimp tanks and the planaria and hydra are still absent from the tank. Every species of shrimp has bred successfully for me to this point, even the Amano Shrimp. However, I have been unsuccessful thus far in raising the Amano larvae. A smaller dose of fenbendazole may be effective against planaria and hydra but I have not experimented with it yet.
'Note: Measuring 0.1 gm of fenbendazole is difficult for most hobbyists. Since it is very insoluble in water, I have suggested to fellow hobbyists that they simply divide one 1 gram packet into ten equal parts and add one of these parts for each 10 gallons of water. So far, everyone has had success using this method. If measuring a 0.1 gram dose is not possible, a water change after 48-72 hours would probably be a good idea. ...'
Thanks to the brilliance of the above people, and to those producing/maintaining the Internet, it's just a question of finding the appropriate stuff and applying it correctly.
That, and identifying the problem...
I still don't know what my thread-hanging critters are.
But I thought this might be useful to some.
are they harmless? I assumed they might have came off some new plants I got recently, couldnt think where else they have come from.
