I built a filter out of a 50 gallon trash can that is hidden in the waterfall. It has a 5 gallon watertight bucket that i drilled holes in, which is sitting on a crate. It's actually filtered 2 times - once through the 5 gallong bucket, and then again when the water exits the bottom of the bucket and goes through microfiber towels and hits sponges in the crate again. It's loaded with sponges/rocks/bioballs/microfiber sponges/etc. The water enters from a hole plumbed in the top. to the 5 gallon bucket, rises up and exits through the water fall. I cut a 14 inch wide by 1.5 inch high cutout for the waterfall. It's completely hidden. I thought it worked out great. It's been keeping the water clear. The pump is 3000gph so there is a decent water flow. I want to add another pump in the pond to have a moving current at the bottom. I put some gold fish in there to help cycle it, along with the water lettuce and they love swimming against the current in the stream, like trout. I'm surprised they even made it up in to the stream.
I thought about it but I can't catch trout for some reason. I can see them in front of me but they never bite. I can catch rockfish, largemouth bass, pike, sunfish, bluefish, white and yellow perch, skate, etc but trout don't like me...lol.