xantha.org

I noticed fairly early on that I was getting some weird white spots on the inside of my fish tank that looked like water spots. Except that of course water spots on the inside under the water level didn’t make much sense.

planaria

In browsing fish forums, I discovered that planaria thrive on high ammonia levels. They are a sign that you have an ammonia problem if you have a stocked tank (good to know!). If you are like me and are cycling a fish tank without fish by using household ammonia, then they pop up during the time that the nitrosomonas bacteria is building up. They will stick around through the fishless cycle because you keep adding ammonia to the tank to keep the nitrosomonas bacteria from dying off while waiting for the nitrobacter to build up. They don’t mention this in any of the fishless cycle tutorials!

The good thing about planaria is that they will die off when the ammonia source goes away. Also many fish like to eat them. They are fairly harmless.