The rated flow rate of all canisters is based on empty can and short hoses. The actual flow deliverable is reduced by resistance of Long hoses, media in the can, and any reactor attached in line. As the media is clogged, the flow will be further and progressively reduced to a trickle if you donít clean it.
If you want good flow to drive the reactor, leave the can empty or filled up with ultra coarse media that can never be clogged. If you want good flow for better circulation purposes, get a dedicated wave maker pump which is the best bang for the buck. If you want undiminished flow, get an HOB. HOBs will deliver the same rated flow at all time because as the media is clogged, the flow will be pushed back to bypass the media and overflow onto the spillway with no reduction.