This has happened twice and I can't figure out how I fixed it last time. The powerhead supplying the calcium reactor from my sump has stopped getting the water to my reactor. It's like the pump can't get the water up and over the sump wall. But it has been running great for a few months. Now suddenly the reactor water level has dropped and I can't get the powerhead to get more water into the reactor. The powerhead is pumping out water like normal. It seems like something is blocking the line somewhere, but it is not blocked. The circulating pump seems to be functioning well. This pump sort of appears to pull some of the water coming in from the sump/powerhead source in as well as recirculating it in the reactor. Since this has happened twice something is up. I still go back to a blockage but I can't figure out where. I have not taken the reactor/pumps/powerhead apart or removed it from the stand, but I guess I need to. What do you all think is up with this, blockage?