I have the same filters on all 4 of my tanks, I also have sand substrate which is why I use these filters because they don't get clogged and stay quite when the fish kick up the sand.
Anyway, like post #6 said clean your filter once a month, that stuff on top when it looks like that, clean it as needed, you do not want that... it is bacterial build up and not the good kind.
I used to clean where the impeller sits.. that little spoke ...but it is very fragile and breaks easily...so I use my sprayer from the sink to clean it. I use a baby bottle brush for all the large parts and a small brush to clean the plastic tubes.
I clean my filters in my kitchen sink, but most say to clean them in dirty tank water to preserve the good bacteria. I never had a problem though...so each his own.
Unfortunately, having to kick start the impeller is the only drawback to this brand.