What I do when I need to get some gunk out of the gravel in my planted tanks is I clean the filter real good. Hook it back up run it for a few minutes then I stir the gravel a bit to get the gunk to float so the filter can get it and I drain the water at the same time. I do that because there are a lot of places where the plants are too close together for me to get the hose inbetween them. If I can I just vaccum the gravel real lightly and call it good. I don't get the gravel real clean, I leave a lot of it there. The plants use it to grow. Rose