paresites on glass

Question
hi chris,
I have a 3 foot,170 ltr tank.
my fish include: 2 hatchets, 4 glass catfish,
and 3 bristlenose catfish.
my bristlenose catfish recently had 2 loads of fry.the first was about 30 fish and the second around 50.with the first load of fry the tank was holding up well, but after the second batch i have noticed worm like peresites and peresites that look like, well tadpoles with 2 prongs from the front of the body and a tail.
these things dont seem to be bothering the fish.
i have since removed the fry from the tank(big mistake).thinking they were external paresites i treated the water with PARA-CIDE(TRICHLOROFON), and after 2 treatments the paresites are still there and in bigger numbers.i gues my question is did i treat my tank correctly or is there a different product i can use to rid my tank of these paresites..
any help would be appreciated.
with regards,
Chris S.

Answer
Hi Krzysztof;

It sounds like planaria or some other harmless scavenger. They cannot be killed with medicines but must be starved out. Their presence is a sign that the gravel is dirty. Vacuum the gravel and make a water change of 25%. Do it again every 2 or 3 days until the gravel is clean while cutting back on food. These little creatures may come out more once you start cleaning out their food source, but it's because they are desperate for food. They will disappear if you keep the waste matter down.

It's possible they are another fairly harmless creature such as hydra. Here are some links to articles and pictures of various creatures;

http://badmanstropicalfish.com/articles/article1.html
http://www.fishpondinfo.com/micro.htm
http://www.waterwereld.nu/platwormeng.html
http://groups.msn.com/FishHealth/planarians.msnw
http://naturalaquariums.com/inverts/worms.html

At Your Service;
Chris Robbins