Planted Tank Guru
Join Date: Jul 2010
Location: Pflugerville, Tx
Since all tanks are different, there is a wide range of when the filter will need cleaning. For a start on deciding, you can take a quick look on the Eheims without disconnecting anything. When it is dark, shine a bright light(LED?) on the canister side and you can often see how much grunge is building up. If it looks full, I clean it but I never get a full year on any of my tanks. 3-6 months is normal for me.
I would see no connection between filter cleaning and algae buildup. I might guess that would be due to phosphate or other nutrient or lighting problems.