weird thread-like worms

Question
Hi, I have a 10 gallon tank with a Jack Dempsey Cichlid named "Jack". I've had the tank for about 7 years, and Jack for about 3 years.  The problem started many years ago when I had 2 convict cichlids, there seemed to be small thread-like worms floating in the water, I cleaned the enitre tank, changed everything, and nothing worked.  The fish seemed healthy and fine. It seemed that over time the problem went away.  Now I have Jack and I recently moved, which made me change 90% of the water, and I think the move has been hard on Jack.  The tap water where I live now, despite treating, has been very cloudy, and requires me to change the filter many more times than I have ever had too.  I decided to use spring water instead of tap, and the water looks much clearer, but the little thread like worms are back. It's hard to tell if Jack is suffering at all, but I tried a parasite-killer pellet, but it's not working.  Any suggestions on what it could be, and how to treat? Thanks for your help!

Answer
Hi Ruth;

The 'worms' are just scavenging planaria or nematodes and are totally harmless to your fish. They don't infect, they are simply doing a job. Their presence is a sign that Jack is getting too much food. They are thriving on the excess waste he makes. That would explain the cloudiness and having to clean the filter so often too.

Vacuum Jack's gravel and replace 25% of the water every couple of days for a week or so while cutting back on food. Use regular tap water, adding a water conditioner. There really isn't any benefit to using spring water in a fish tank, unless your tap water isn't safe for some definite reason. It's so much easier to use tap water anyway.

Planaria cannot be killed, only starved out. Before I knew how harmless they were years ago I even used bleach in a tank (took the fish out of course), let it circulate for 2 hours and the little critters were still alive in there! Pretty indestructible until you take their food away. You may see more of them at first but it's not because they are multiplying. It's because they usually hide in the gravel and decorations, and once their food is less available they get desperate and come out looking for more. They will begin to die off and your gravel vacuuming will remove the dead bodies as well as many live ones, along with the excess crud they thrive on.

Hope all goes well!

At Your Service;
Chris Robbins