The grey lever on the 407 is flow control. Parallel with the floor is wide open, perpendicular is off. If you raise it all the way up like it is in your image then flow will be off. Then you raise the red lever to disconnect the hoses from the filter for maintenance.
Thanks for the suggestions the filter seems to be working well. Cycling the tank is proving much harder than I had thought and I am not dealing with Ammonia levels much higher than I would like. At this point water changes is what I am going for to bring it back down. I started with a fishless...
First post! My wife runs a daycare and we are starting up a 75 gallon tank. We have built a stand so the tank is about ten inches off the ground. The kids have been really good with the 37 gallon tank we have had for years and like to sit and look at the fish. It also serves as good night...