When an external canister filter should be cleaned is dependant on a number of things. One important criterion is the flow rate. This can already be measured on some EHEIM external canister filters on the pump head (professionel II or professionel 3 models).
With the new flow rate indicator, you can read the flow rate quickly and easily on the aquarium hood.
The red indicator shows the rate of throughflow. The grey ring on the indicator can be positioned to indicate flow rate immediately after cleaning.
Thus flow rate reduction over time can be seen at a glance.
The new flow rate indicator fits simply into the overflow in place of the cap.