white spots/ worms in tank killing fish

Question
Hey Chris,
   I have recently seen Little white spots on the sides of my tank and worms occasionally creeping around the tank. So far two tiger Oscars have died. There's only on Albino Oscar left alive in the tank and is showing the signs the tigers did before they died. I do 20% water changes twice a week and have a PH of 7.0, ammonia levels of 1.1 and nitrate levels of 0.1. What do you think this parasite/critter this is? Thanks for your time.

 -Zach

Answer
Hi Zach;

What a shame. I'm so sorry for the loss of your other two. Hopefully we can save the last one. Those little creatures are a symptom of dirty gravel and are probably planarians or nematodes of some type. They feed on decaying organic matter so when there is plenty, they go crazy. The critters themselves are not actually harming your fish. They only feed on excess waste and decaying food, not live fish. The cause of their overpopulation is what is harmful. Your ammonia levels are elevated too which is another symptom of trouble going on. Cut back on food, make a 25% water change and vacuum the gravel. Oscars are big messy guys and need a gravel vacuuming once a week. Replacing water is a very good thing to do, but if there is too much solid waste in there it has to be removed too.

Once the gravel is cleaned and kept clean the little critters will slowly starve out and most go away. Most tanks already have these little things but we don't actually see them unless waste gets out of control and they reproduce until are so many that they show up everywhere. When you first start cleaning it might look like there are more of them than ever. It's just that they are starving and trying to find the waste you are getting rid of so they are exposed more. Trying to use chemicals or medicines to kill them is totally useless. They are nearly indestructible and will even survive bleach and hot water so your fish would die before it hurt the tiny critters. Their food source has to be removed to control them.

Overcrowding, inadequate filtration, and too small a tank can all contribute to this trouble too. Let me know what size your tank is, how long it has been set up, what kind of filtration, how big your fish were/are, what kind of food, how often and how much food, etc., and I can help you get things fixed up.

At Your Service;
Chris Robbins