I can understand your frustration cleaning out those kinds of filters as they are cumbersome and awkward to get to. The green stuff will accumulate. My opinion is that there is but one thing to do and that is to make the cleaning of filters easier by making them more accessible. That, along with creating a settling tank before the filters to allow much of the "gunk" to settle out before the filters, will make life much easier. I installed a concrete filter box with vertical slots in it that accept half sheets of Matala mat filters. When they get filled with gunk, I simply lift them out vertically, wash them off with a hose and slip them back in. It takes less than a minute to clean the filter elements in that configuration.
Don Perry