freshwater fish disease

Question
I have a 90 gallon freshwater tank set up with south american cichlids.  The tank has been set up for 6 years but has been taken down and moved from one house to the most recent residence.  That was about a year ago.  We have added two fish since then.  One from a friend an Oscar but he was in a tank by himself.  The other fish is a silver dollar from a fish store.  I have 8 fish in the tank.  The filters are two canister filters.  All the ph, nitrate, and ammonia levels are normal.  We change the water once a month on average and about 25 gallons replaced at a time.  Here recently in the past two weeks I have noticed some white worm looking parasites floating around in the water.  They range from an eighth of an inch to a half inch in length.  I haven't seen any attaching themselves to the fish or attacking them but I have had two fish die.  I raised the temperature and treated them with an ich medicine but it hasn't helped.  I am not sure what they are or what treatment needs to be done.  I have seen some of the parasites in the feces of the fish.  What can I treat the whole tank with and is it too late?

Answer
Hi Jamie;

They are actually just harmless creatures like planarians or nematodes. They aren't a danger to the fish themselves, but the reason they are multiplying is definitely dangerous. They are in the feces because that's what they feed on; decaying organic waste. They can't be killed by using medicines or chemicals, they have to be starved out. Cichlids are very messy guys that make lots of waste and there is waste building up in there. All tanks need a 25% water change and gravel vacuuming once a week every week, especially the messy types. If your gravel is deeper than an inch you may have to remove some so that waste doesn't get trapped under there between cleanings.

To get the tank straightened out quickly and help avoid the loss of more fish, make a series of water changes and vacuuming. Replace 25% of the water while vacuuming every other day for the next week. Cut back on food by 50% until things are doing better too. Your fish will not starve, they are fine even with no food at all for more than two weeks.  You may see more of the white worms at first, but don't be discouraged.  They like to hide but more will come out looking for food as you remove their food source. Keep at it and most of them will go away. Many of our tanks have them present all the time so some will probably stay. They can serve as a warning sign that we are overfeeding or our tank is overcrowded. If you see several of them again, cut back on food and clean more again.

Once the tank is cleaned up and you see fewer of the little worms you can do weekly cleanings and just keep it maintained doing that. Feed less food than you did originally and everything will probably work out just fine. Sometimes a change in brand or type of food helps too.

I hope it all goes well...

At Your Service;
Chris Robbins

http://www.kasamba.com/fish-expert-chris