The low flow rate is probably brought about by air trapped in the filter or a kink in the hose. Try putting the outlet of the filter into a bucket sitting next to, or lower than the filter. Then gently tap the filter casing and see if any air comes out. (*NB* Have the power turned OFF when you do this).
If that doesn't work then remove the filter materials and set the filter back up without any media in it. Then try running it. If it still doesn't run properly then there is something wrong. A dirty impellor or blockage in one of the hoses will cause problems and reduced flow rates.
If it does work then put the filter materials in one at a time, and turn the filter on after each type of media has been added.
Personally I would replace one lot of ceramic beads with a sponge and not bother having carbon in it. Carbon removes chemicals from water, including plant fertiliser and medications. It also clogs up quickly and should be replaced every month. Unless you have lots of chemicals in your water supply I wouldn't bother about the carbon. Instead just have a layer of filter wool, but use the Dacron type, not the fluffy filter wool. The Dacron type is like a flat sheet that is pretty tough and won't come apart under water. The fluffy filter wool can lose bits that get caught up in the impellor and cause damage to the motor.
