I have an MSR "trailshot" hand-pump water filter which works well for me on trips where I've felt the need for such a thing.
Unfortunately, after some usage in what turned out to be a rather slimy lake, the intake filter (which I think is sometimes called the "macroscopic" or "mechanical" filter) is in a bit of a sorry state and all gunked up and the device doesn't work as well as it used to. Here's a couple of photos from each side of it:
All the clogging seems to result in the water filter's chamber being slow to refill in the expansion phase (compared with how it used to work when the intake filter was clean). The compression phase which drives water through the main filter cartridge works fine, and if I remove the intake filter it seems to function as freely as I remember it doing before it got gunked up (which is all very well pumping tap water as a test, but obviously that'd be highly undesirable to use it like that "in the field").
MSR do sell replacements but so far as I can find only accompanying a full main filter cartridge (which I don't think I need yet), and at ~2/3 the price of a new device (example vs. example) it seems overkill.
Any suggestions how to best clean this filter up? Washing it or lightly rubbing it with a finger or a cloth does nothing. Poking at it with a pin (as yet untried) might work better... but would take forever. Something a bit more mechanically and/or chemically powerful maybe? I think the fact the gunk is organic (algae?) is part of the problem; the filter has been degraded by silt/sand before but that always washed out relatively easily.