Copied directly from the eheim website:
A. Maintenance is comprised of two separate tasks, media maintenance and filter maintenance.
Your 2211, 2213, 2215, 2217 needs to be cleaned every 3-6 months.
You should change 1/3 * 2/3 of the EHFISUBSTRAT every 6-12 months.
The EHFISYNTH pad should be changed with every cleaning (every 3-6 months)
and the EHFIFIX pad should be changed when it becomes flattened or every year.
Filter Care and Maintenance:
EHEIM pumps and filters have been designed to offer the user many years of service with minimal maintenance required. However, if your EHEIM filter is to be reliable and operate fault-free for many years, they do need a little care.
Following are some tips on filter and pump maintenance. The following is best undertaken when you change your filter media.
Rinse the filter canister and the two lattice screens with water and remove any adhering dirt residues. Before the pump head is replaced, check the rubber o-ring. If it is worn it should be replaced immediately. If it is not worn, it should be moistened so that the pump head can be pressed down without difficulty.
The water inlet of the canister should be cleaned with an EHEIM cleaning brush. At longer intervals (every six months or when build up of debris is seen), the hose system should be cleaned. The EHEIM flexible cleaning brushes are specially designed for this. The nylon thread attached to the brush is threaded through the hose and then pulled through. In this way the valves do not need to be removed.
The pump of your EHEIM filter also requires some regular maintenance. Remove all parts carefully and clean all parts with a mild dishwashing soap and then thoroughly rinse with water making sure that no soap remains.
Clean the cooling pipe and the impeller chamber with the EHEIM brush kit item no. 400955. Replace all parts in reverse order of dissemble. For models 2211 and 2213, when replacing the cooling pipe shaft, ensure that it is pushed in until it is flush and locked into place.
IMPORTANT: if your pump is extremely dirty and the impeller and associated parts are hard to remove, soak the complete pump head in warm water and mild dishwashing soap overnight. You should never force the removal of these parts, as they are fragile.