Worms in Tank??

Question
20gal freshwater,  2 oscars, tank over a year old, last 2 wks get these little clear/wht tubes/worms?? 1/16th 1/32 in size?? on glass, killed the first set with ich treatment/tank cleaning. a week or so later there back.  Never had snails or live plants (oscars) what are they?? and how do i get rid of them

Answer
Hi Dan,
These worms are very common, especially in cichlid tanks -- particularly oscars! ;-)

These are harmless scavengers known as "Planaria" that feed on excess food and nutrients in the water. And whenever the food supply sudden expands or remains at a high level, they will explode in their numbers and be every in the tank, even on the fish!

Though they are harmless themselves, their presence means that the aquarium has too much nutrient buildup and high nitrates. Which of course is bad for your fish. Unfortunately two oscars in a 20 gallon is very overcrowded and with only the fishes best interest in mind, it would be better if you got them into a bigger tank as soon as you can. Otherwise, unless you do daily 100% water changes the poor fish will pollute their water too much and cause all sorts of health problems like stunted growth and hole-in-the-head. I'm not trying to drill you. But I would just hate to see your oscars suffer these or perhaps even more problems due to too-small aquariums.

The best cure for Planaria is an aggressive water change schedule. Medications are not necessary and they can be stressful to the fish.
Change about 50% of the tank's water everyday. Make sure to gravel vacuum thoroughly. And insure all replacement water is equivalent in temperature to your oscar's tank and don't forget water conditioner.

Water changes will deplete the worms food supply and the worms themselves but the problem may keep coming back because of the high bioload you have in your tank. Keeping up with big 50-75% twice to three times a week water changes is best. A larger aquarium wouldn't require as much. Although not ideal a 55 gallon tank would be so much better. Two full-grown oscars would thrive best in an 80-100gallon tank. These guys get big and need so much room its incredible.They require quite a devotion. ;-)

Best wishes and I hope this helps!
Karen~