Be very careful about cleaning filters out. A well designed filter has separate functions for removing solid matter and for providing a substrate for filter bacteria to grow on. Say brushes or foam for the former and gravel or plastic rings for the latter. You ONLY want to clean out the solids removal media. A lot of filters use foam for both, which I don't really agree with, but if that is the case you must only over clean it out with pond water, never with chlorinated tap water. Just stick it in a bucket and squeeze it out.
I think for the stocking density you've got, you want your filtration to be top notch.
Adding another filter will do only good, by the way, so well done with that. Thanks boy