Use of aquatic insects/crustaceans or other to actively clear the gravel filtration beds of debris.

Hi Permies.

I'm planning an organic pool.  Although I was inspired by David Pagan Butler's ideas, I will not be following his typical build.  I am approaching it something more like a conventional pool, although I will be incorporating the airlift means of circulating the water.  My plans include a singular, large vertical pipe with which to move a column of water which will then be divided into two pipe sections that will carry the water in two different directions down into the filtration beds. As I imagine it, the beds will consist of larger stones on the bottom and will be covered with stones increasingly smaller in size until the last few inches or so that will consist of pea gravel.  So in this pool, the water will rise from the bottom of the filtration bed, up through the stones and gravel until it reaches the surface.  I have read that some natural pools that filter from the top down have developed a problem with the beds getting clogged up with debris.  It is my hope that the bottom up approach might prevent this.  Now, to the point of this post.  Is it possible that certain organisms could be employed to assist in keeping the gaps between the stones and gravel clear?

If so, what kind of organisms/species?
I'm thinking of some kind of freshwater shrimp, but IDK.  I live in zone 6B and Winter can be somewhat hostile here.

I've tried red worms and I've tried aquatic snails.  In my case, the worm population collapses.  I think this is due to the cinder rock mixed into my media.  Maybe, it's too abrasive.  The snails clean up algae and biofilms, but they also contribute to the poop that builds up in the media beds.  Some fish will eat the snails, too, so that's a bonus.  Another downside, however, is that aquatic snails can be liver fluke vectors.  

Eventually, my media beds clog up.  Typically, it takes two years.  What I do now is to run a filter between the fish tank and media beds.  This way, the media functions for nitrification, but not so much for filtration.  Every few months, I use an airlift to pump the fish poop sludge into another tank for remineralization.  It's kind of like making tea from worm castings.  You can add molasses as a carbon source.  I aerate the shit out of it for a month.  Photoheterotrophs (I think) break down the fish poop.  Nutrients that plants crave are contained within the bodies of the microbes.  After a month to a month and half, I turn off the aerator and let it settle out until it is clear.  Then, I add the clarified nutrient rich water back to the system.  

This process makes system maintenance easier and reduces costs because you are producing your own plant supplements.