First make sure you have not lost your siphon. If you have not, then open up the cannister and clean the impeller and make sure it is ok and set right. Hopefully it is ok and restarts for you. I had this happen to me once and it turned out my shaft was broken and needed replaced.
__________________ From where the sun now stands, I will fight no more forever.
Yes it still has a syphon i think, well when i pull the bar off that returns the water back into the tank a little bit of water flows out. What should i do so that the water that is renturned comes out with the correct amount of water and not a small amount. i am afraid tha if i open the canister up then water will be fowing trhough it. What would you suggest i do.