Those tiny wiggly worms in your tank !
I see a lot of desperate pleas for help so I decided to post some information from elsewhere. May not agree with everything there but its a good guide in general.
Planaria
What are Planaria?
Have you ever looked into your tank and seen tiny little white things wriggling through the water or crawling on your glass? If so, you are likely seeing Planaria. Planaria are a type of flatworm; Platyhelminthes phylum.
Before you get too upset about having flatworms in your aquarium, take a deep breath. Planaria are harmless to your fish. But don't get too complacent about their presence, either. There are a few things you should be aware of . . .
Why are They in My Tank?
Planaria tend to crop up in aquariums where there is an excess of food and waste decaying in the gravel beds. This rotting waste is their food source. So you see, while the planaria themselves are harmless they are a symptom of a larger problem.
This problem being, specifically, that uneaten food and fish waste releases ammonia as it rots. Ammonia is toxic and often lethal to fish. In a well-maintained and cycled aquarium the normal output of ammonia from uneaten food and fish waste is converted to less harmful substances by the colonies of good nitrifying bacteria built up in the tank. However, if you're seeing planaria then chances are that the problem has gone on long enough that the nitrifying bacteria is no longer present and your ammonia, nitrite, or nitrate levels are almost surely at a dangerous level now. Your fish may be experiencing health problems, behavioral changes, and ammonia poisoning at this point. As you've realized by now, planaria are warning signs that you need to re-evaluate your tank maintenance routine.
How Do I Get Rid of Them and Fix My tank?
The only real way to get rid of them is to remove their food source, striking at the root of the problem. To do this you'll need to do the following things:
* do 15-25% water changes every day for the next week
* Make sure you use a gravel vacuum when doing water changes so that you know you're getting it clean. If you never use a gravel vacuum, that's part of your problem.
* You may have too much gravel in your tank. If this is the case it is providing too much space for food/waste to decay in. That makes it harder to clean during water changes and harder for the filter to suck out particles. You should never exceed 1/4 of an inch of gravel on the bottom of your tank. If you have more than that, you'll need to get rid of some.
* Adding aquarium salt can help in some cases also. (Do not exceed 1 tablespoon per 5 gallons of water). However, if you keep invertibrates or scaleless fish in your tank you should skip on the salt as it can hurt or kill them.
* Test you ammonia, nitrite, and nitrate levels every day to ensure that they go down and stay in safe levels.
How To Make Sure They Don't Come Back
If you're having planaria problems it's time to start trouble-shooting your maintenance methods. Below are some of the things you should be doing on a regular basis to keep your tank healthy and planaria-free:
* weekly 25% water changes
* using a gravel vacuum each and every time you do water changes
* Don't overfeed your fish. You should only feed them as much as they can eat in 5 minutes. If you're seeing a substantial amount of food left over after they're done eating it's time to start cutting back.
* Test your ammonia, nitrite, and nitrate levels once a week. If you start to see you nitrates climbing (or heaven forbid, your nitrites or ammonia) you'll need to do some water changes.
* Make sure you don't have too much gravel. You only need 1/4 of an inch evenly spread.
