Hi,
I own a 2215 filter, once i had issue with the flow and tried lot of things nothing helped when i take to service center there they found one broken ceramic ring got stuck in the inlet tube where it attaches to the canister when they removed that it started working perfect, and also make sure there is no air inside canister this will reduce the flow to check just tilt and see for any air lock is there or not, and before priming make sure there is no water inside canister, and also just remove your impeller and put it back once. what is your the MM size of your lily pipe looks like big in the video, and like Clive said you can use 2217 impeller for increasing flow even before i got my second canister i was using boyu submersible pump1600 per litre impeller for 2 months worked very well with high flow. now I'm using original impeller with 10mm lily pipe outlet, my flow is good.