Pool filter for Duck pond

[Ruralhideaway]

So, the water goes in the water trough at the bottom and then filters up through 100 gallons worth of lava rock and pours over the edge of the tub back into the pond (I know through the pretty waterfall feature, but essentially) correct?

Actually its plumbed over the side to the bottom, freeing the built in bottom drain to allow release of sludge.

 

[Kiwibird]

Lots of us use kiddie pools or half barrels for our ducks. Does anyone have tips for keeping those cleaner? Even halving my water use would be more eco-friendly.