Right. It is a waste of time treating the top when the pots sides are not. But if you treat the pot thoroughly with a dunk solution, it will kill them off. The nematodes are voracious eaters. They survive and migrate in very little liquid so there is no need to over water. A quarter piece in a quart bottle of water with a hole in the cap. Squeeze out a few good shots before feeding then water it in with the feed solution. Keep topping off the bottle. It may take a couple few feeds to get the whole pot but it will handle them. Throwing a quarter piece into the runoff pan helps too.