I have 6 tanks currently set up at my house and 3 at the place I volunteer at.
Yah, I have noticed that the filter, with all the current that it produces, moves a lot of the dirt under the rocks and wood or directly into the intake nossle. I did have gravel in all the tanks until last summer when I was going to put sand in. Now I'm not sure what substrate I want so there is nothing in the tanks. Thanks for looking