Anyone have an eheim pro canister filter?
i was wondering when you are supposed to change the substrate in the tank? i have looked in the manual and just about everywhere online and cant seem to find a good answer =]
also does anyone know how long a new tank with this filter will take to cycle?
Quick answer is never.
Once the cycling is complete, the substrate will mature. This means it will be full beneficial or nitrifying bacteria. If you change the substrate, ,your tank will have to go through the cycling process again. So you should never change the substrate unless it is absolutely necessary.
EDIT
Having written the above, I realized the question is concerning canister filter. The substrate you are referring to is the filter media in the canister. This substrate or the filter media should also never be replaced. You could rinse it in the aquarium freshwater during maintenance.