I just have come upon this problem. My cartos work great at first in a tank. After a few days its like sucking wet quicksand. So I switch cartos and clean the one flushing with a syringe and boiled water. Now, while doing this my 5ohm cartos never have a flooding problem but when I switch to 3.0ohm they just flood within about 10 minutes. I know how to unflood them by spinning them but I want to know why they are flooding in the first place. Thanks everyone.